Light source device and projector

ABSTRACT

A light source device includes a light source, an optical element for transmitting light from the light source which is polarized in a first polarization direction and reflecting the light polarized in a second polarization direction, a polarization split element for transmitting the light from the optical element which is polarized in first polarization direction and reflecting the light polarized in the second polarization direction, a wavelength conversion element for performing wavelength conversion on the light to emit second light in a second wavelength band, a diffusion element for diffusing the light, a first color separation element for separating light from the polarization split element into third light in a first wavelength band and fourth light in the second wavelength band, and a second color separation element for separating light from the optical element into fifth light in a third wavelength band and sixth light in a fourth wavelength band.

The present application is based on, and claims priority from JPApplication Serial Number 2020-156177, filed Sep. 17, 2020, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a light source device and a projector.

2. Related Art

There has been known a projector which modulates light emitted from alight source to generate image light based on image information, andthen projects the image light thus generated. In JP-A-4-60538 (Document1), there is disclosed a projection type color image display deviceprovided with a light source, a plurality of dichroic mirrors, a liquidcrystal display element having a microlens array, and a projection lens.The projection type color image display device separates the white lightemitted from the light source into a plurality of colored light beamshaving respective colors different from each other, and then makes thecolored light beams thus separated from each other enter the respectivesub-pixels different from each other in one liquid crystal displayelement to thereby perform color display.

In the projection type color image display device described above, thereare arranged a red reflecting dichroic mirror, a green reflectingdichroic mirror, and a blue reflecting dichroic mirror along theincident light axis of the white light emitted from the light source ina state of being nonparallel to each other. The white light emitted fromthe light source passes through the dichroic mirrors described above tothereby be separated into red light, green light, and blue lightdifferent in proceeding direction from each other. The red light, thegreen light, and the blue light respectively enter red sub-pixels, greensub-pixels, and blue sub-pixels of the light modulation element in thestate of being spatially separated from each other by a microlensdisposed at the incidence side of the light modulation element.

In the projection type color image display device in Document 1, a lamplight source such as a halogen lamp or a xenon lamp is adopted as thewhite light source, and a liquid crystal display element is adopted asthe light modulation element. Although the light emitted from the lamplight source is unpolarized light, when using the liquid crystal displayelement as the light modulation element, the light entering the liquidcrystal display element needs to be linearly polarized light having aspecific polarization direction. To this end, it is conceivable todispose a pair of multi-lens arrays for dividing the incident light intoa plurality of partial light beams, and a polarization conversionelement for uniforming the polarization directions of the plurality ofpartial light beams between the white light source and the liquidcrystal display element as a device for homogenously illuminating theliquid crystal display element. In this case, there is generally used apolarization conversion element provided with a plurality ofpolarization split layers and a plurality of reflecting layersalternately arranged along a direction crossing the incident directionof the light, and a retardation layer disposed in a light path of thelight transmitted through the polarization split layers or a light pathof the light reflected by the reflecting layers.

However, when reducing the projection type color image display devicedescribed above in size in compliance with the recent demand ofreduction in size, it is difficult to manufacture the polarizationconversion element narrow in pitch between the polarization split layerand the reflecting layer. Therefore, it is difficult to reduce the sizeof the light source device equipped with this type of polarizationconversion element, and by extension, to reduce the size of theprojector equipped with the light source device. In view of such aproblem, it is required to provide a light source device capable ofemitting a plurality of colored light beams uniformed in polarizationdirection without using the polarization conversion element narrow inpitch.

SUMMARY

In view of the problems described above, a light source device accordingto an aspect of the present disclosure includes a light source sectionconfigured to emit a first light beam which has a first wavelength bandand includes light polarized in a first polarization direction and lightpolarized in a second polarization direction different from the firstpolarization direction, an optical element which is configured totransmit the first light beam entering the optical element from thelight source section along a first direction and polarized in the firstpolarization direction toward the first direction, and is configured totransmit the first light beam polarized in the second polarizationdirection toward the first direction, a polarization split element whichis disposed at the first direction side of the optical element, which isconfigured to transmit the first light beam entering the polarizationsplit element along the first direction from the optical element andpolarized in the first polarization direction toward the firstdirection, and which is configured to reflect the first light beampolarized in the second polarization direction toward a second directioncrossing the first direction, a wavelength conversion element which isdisposed at the second direction side of the polarization split element,which is configured to perform wavelength conversion on the first lightbeam entering the wavelength conversion element along the seconddirection from the polarization split element, and polarized in thesecond polarization direction, and which is configured to emit a secondlight beam having a second wavelength band different from the firstwavelength band toward a third direction as an opposite direction to thesecond direction, a diffusion element which is disposed at the firstdirection side of the polarization split element, and which isconfigured to diffuse the first light beam entering the diffusionelement along the first direction from the polarization split element,and which is configured to emit a result toward a fourth direction as anopposite direction to the first direction, a first color separationelement which is disposed at the third direction side of thepolarization split element, and which is configured to separate lightemitted from the polarization split element into a third light beamhaving the first wavelength band and a fourth light beam having thesecond wavelength band, and a second color separation element which isdisposed at the third direction side of the optical element, and whichis configured to separate light emitted from the optical element into afifth light beam having a third wavelength band different from thesecond wavelength band, and a sixth light beam having a fourthwavelength band different from the second wavelength band and the thirdwavelength band, wherein the polarization split element transmits thesecond light beam polarized in the first polarization direction towardthe third direction and reflects the second light beam polarized in thesecond polarization direction toward the fourth direction, and theoptical element reflects the second light beam which enters the opticalelement along the fourth direction from the polarization split elementand which is polarized in the second polarization direction toward thethird direction.

Further, a light source device according to another aspect of thepresent disclosure includes a light source section configured to emit afirst light beam which has a first wavelength band and includes lightpolarized in a first polarization direction and light polarized in asecond polarization direction different from the first polarizationdirection, an optical element which is configured to transmit the firstlight beam entering the optical element from the light source sectionalong a first direction and polarized in the first polarizationdirection toward the first direction, and is configured to transmit thefirst light beam polarized in the second polarization direction towardthe first direction, a polarization split element which is disposed atthe first direction side of the optical element, which is configured totransmit the first light beam entering the polarization split elementalong the first direction from the optical element and polarized in thefirst polarization direction toward the first direction, and which isconfigured to reflect the first light beam polarized in the secondpolarization direction toward a second direction crossing the firstdirection, a diffusion element which is disposed at the second directionside of the polarization split element, and which is configured todiffuse the first light beam entering the diffusion element along thesecond direction from the polarization split element, and which isconfigured to emit a result toward a third direction as an oppositedirection to the second direction, a wavelength conversion element whichis disposed at the first direction side of the polarization splitelement, which is configured to perform wavelength conversion on thefirst light beam entering the wavelength conversion element along thefirst direction from the polarization split element, and polarized inthe first polarization direction, and which is configured to emit asecond light beam having a second wavelength band different from thefirst wavelength band toward a fourth direction as an opposite directionto the first direction, a first color separation element which isdisposed at the third direction side of the polarization split element,and which is configured to separate light emitted from the polarizationsplit element into a third light beam having the first wavelength bandand a fourth light beam having the second wavelength band, and a secondcolor separation element which is disposed at the third direction sideof the optical element, and which is configured to separate lightemitted from the optical element into a fifth light beam having a thirdwavelength band different from the second wavelength band, and a sixthlight beam having a fourth wavelength band different from the secondwavelength band and the third wavelength band, wherein the polarizationsplit element transmits the second light beam polarized in the firstpolarization direction toward the fourth direction and reflects thesecond light beam polarized in the second polarization direction towardthe third direction, and the optical element reflects the second lightbeam which enters the optical element along the fourth direction fromthe polarization split element and which is polarized in the firstpolarization direction toward the third direction.

A projector according to an aspect of the present disclosure includesthe light source device according to the aspect of the presentdisclosure, a light modulation device configured to modulate light fromthe light source device in accordance with image information, and aprojection optical device configured to project the light modulated bythe light modulation device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a projector according toa first embodiment.

FIG. 2 is a perspective view of a light source device according to thefirst embodiment.

FIG. 3 is a plan view of the light source device viewed from a +Ydirection.

FIG. 4 is aside view of the light source device viewed from a −Xdirection.

FIG. 5 is aside view of the light source device viewed from a +Xdirection.

FIG. 6 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

FIG. 7 is an enlarged view of a light modulation device.

FIG. 8 is a side view of a light source device according to a secondembodiment viewed from the +X direction.

FIG. 9 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

FIG. 10 is a plan view of a light source device according to a thirdembodiment viewed from the +Y direction.

FIG. 11 is a side view of the light source device viewed from the −Xdirection.

FIG. 12 is a side view of the light source device viewed from the +Xdirection.

FIG. 13 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

FIG. 14 is a side view of a light source device according to a fourthembodiment viewed from the −X direction.

FIG. 15 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A first embodiment of the present disclosure will hereinafter bedescribed using FIG. 1 through FIG. 7.

FIG. 1 is a schematic configuration diagram of a projector 1 accordingto the present embodiment.

It should be noted that in each of the drawings described below, theconstituents are shown with the scale ratios of respective sizes setdifferently between the constituents in some cases in order to make eachof the constituents eye-friendly.

The projector 1 according to the present embodiment modulates the lightemitted from a light source device 2 to form an image corresponding toimage information, and then projects the image thus formed on aprojection target surface such as a screen in an enlarged manner. Inother words, the projector 1 modulates the light emitted from the lightsource device 2 with a single light modulation device 6 including asingle liquid crystal panel 61 to thereby form the image, and thenprojects the image thus formed. The projector 1 is a so-calledsingle-panel projector.

As shown in FIG. 1, the projector 1 is provided with the light sourcedevice 2, a homogenization device 4, a field lens 5, the lightmodulation device 6, and a projection optical device 7. The light sourcedevice 2, the homogenization device 4, the field lens 5, the lightmodulation device 6, and the projection optical device 7 are disposed atpredetermined positions along an illumination light axis Ax. Theillumination light axis Ax is defined as an axis along the proceedingdirection of the principal ray of the light L emitted from the lightsource 2.

The configuration of the light source device 2 and the homogenizationdevice 4 will be described later in detail.

The field lens 5 is disposed between the homogenization device 4 and thelight modulation device 6. The field lens 5 collimates the light Lemitted from the homogenization device 4, and then guides the result tothe light modulation device 6.

The projection optical device 7 projects the light modulated by thelight modulation device 6, namely the light forming the image, on theprojection target surface (not shown) such as a screen. The projectionoptical device 7 has a single projection lens or a plurality ofprojection lenses.

In the following description, the axis parallel to the proceedingdirection of the light emitted from the light source device 2 along theillumination light axis Ax is defined as a Z axis, and the proceedingdirection of the light is defined as a +Z direction. Further, two axeseach perpendicular to the Z axis, and perpendicular to each other aredefined as an X axis and a Y axis. Out of the directions along theseaxes, an upper side in the vertical direction in the space in which theprojector 1 is installed is defined as a +Y direction. Further, theright side in the horizontal direction when viewing an object which thelight enters along the +Z direction so that the +Y direction points theupper side in the vertical direction is defined as a +X direction.Although not shown in the drawings, an opposite direction to the +Xdirection is defined as a −X direction, an opposite direction to the +Ydirection is defined as a −Y direction, and an opposite direction to the+Z direction is defined as a −Z direction.

The +X direction in the present embodiment corresponds to a firstdirection in the appended claims. The −Z direction in the presentembodiment corresponds to a second direction in the appended claims. The+Z direction in the present embodiment corresponds to a third directionin the appended claims. The −X direction in the present embodimentcorresponds to a fourth direction in the appended claims.

Configuration of Light Source Device

FIG. 2 is a perspective view of the light source device 2 according tothe present embodiment. FIG. 3 is a plan view of the light source device2 viewed from the +Y direction.

As shown in FIG. 2 and FIG. 3, the light source device 2 emits the lightL for illuminating the light modulation device 6 toward a directionparallel to the illumination light axis Ax, namely the +Z direction. Thelight L emitted by the light source device 2 includes a plurality ofcolored light beams which are linearly polarized light beams having auniform polarization direction, and are spatially separated from eachother. In the present embodiment, the light L emitted by the lightsource device 2 consists of four light beams each formed of S-polarizedlight. The four light beams correspond to a blue light beam BLs, ayellow light beam YLs, a green light beam GLs, and a red light beam RLs.

The light source device 2 has a light source section 21, an opticalelement 22, a polarization split element 23, a first retardation element24, a first light collection element 25, a diffusion device 26, a secondlight collection element 27, a wavelength conversion element 28, a firstcolor separation element 29, a fourth retardation element 30, areflecting element 31, and a second color separation element 33.

It should be noted that the P-polarized light in the present embodimentcorresponds to light polarized in a first polarization direction in theappended claims. The S-polarized light in the present embodimentcorresponds to light polarized in a second polarization direction in theappended claims. Further, as described later, the orientation of a filmfor separating the polarization components or the colored light beams isdifferent between a group consisting of the optical element 22 and thepolarization split element 23, and a group consisting of the first colorseparation element 29 and the second color separation element 33.Therefore, the descriptions of P-polarized light and S-polarized lightin the present embodiment represent the polarization direction withrespect to the optical element 22 and the polarization split element 23,and are reversed in the polarization direction with respect to the firstcolor separation element 29 and the second color separation element 33.

Further, in each of the drawings, the P-polarized light is representedby a dotted-line arrow, the S-polarized light is represented by a solidarrow, and light in other polarization states than the P-polarized lightand the S-polarized light is represented by a dashed-dotted-line arrow.

In other words, the P-polarized light with respect to the opticalelement 22 and the polarization split element 23 corresponds to theS-polarized light with respect to the first color separation element 29and the second color separation element 33. The S-polarized light withrespect to the optical element 22 and the polarization split element 23corresponds to the P-polarized light with respect to the first colorseparation element 29 and the second color separation element 33. Itshould be noted that since there is a possibility that the descriptiongets confusing when changing the name of one type of light in accordancewith the element which the polarized light enters, the P-polarized lightand the S-polarized light are hereinafter described as the polarizationdirection with respect to the optical element 22 and the polarizationsplit element 23 without changing the name of the polarized light inaccordance with the element which these types of polarized light enter.

Configuration of Light Source Section

The light source section 21 emits the blue light beams BLs, BLp whichenter the optical element 22 along the +X direction. The light sourcesection 21 has a plurality of light emitting elements 211, a pluralityof collimator lenses 212, and a rotary retardation device 213. The lightemitting elements 211 are each formed of a solid-state light source foremitting the blue light beam BLs. Specifically, the light emittingelements 211 are each formed of a semiconductor laser for emitting theblue light beam BLs as the S-polarized light. The blue light beam BLs isa laser beam having a blue wavelength band of, for example, 440 through480 nm, and having a peak wavelength within a range of, for example, 450through 460 nm. The blue wavelength band in the present embodimentcorresponds to a first wavelength band in the appended claims. The bluelight beams BLs, BLp in the present embodiment correspond to a firstlight beam in the appended claims.

In the case of the present embodiment, the plurality of light emittingelements 211 is arranged along the Z axis. Although the light sourcesection 21 in the present embodiment has two light emitting elements211, the number of the light emitting elements 211 is not limited, andthe number of the light emitting elements 211 can be one. Further, thearrangement of the plurality of light emitting elements 211 is notlimited as well. Further, the light emitting elements 211 are arrangedso as to emit the blue light beams BLs as the S-polarized light, but canbe arranged so as to emit the blue light beams as the P-polarized lightsince a light intensity ratio between the S-polarized light and theP-polarized light can arbitrarily be set by the rotary retardationdevice 213. In other words, it is possible for the light emittingelements 211 to rotate as much as 90° centering on the emission opticalaxis.

The plurality of collimator lenses 212 is disposed between the pluralityof light emitting elements 211 and the rotary retardation device 213.The collimator lenses 212 are disposed so as to correspond one-to-one tothe light emitting elements 211. The collimator lens 212 collimates thelight beam BLs emitted from the light emitting element 211.

The rotary retardation device 213 has a second retardation element 2131,and a rotation device 2132. The second retardation element 2131 is maderotatable centering on a rotational axis along a proceeding direction ofthe light entering the second retardation element 2131, namely arotational axis parallel to the X axis. The rotation device 2132 isformed of a motor and so on, and rotates the second retardation element2131.

The second retardation element 2131 is formed of a ½ wave plate or a ¼wave plate with respect to the blue wavelength band. A part of the bluelight beam BLs as the S-polarized light having entered the secondretardation element 2131 is converted into the blue light beam BLp asthe P-polarized light by the second retardation element 2131. Therefore,the blue light beam having been transmitted through the secondretardation element 2131 turns to light in which the blue light beam BLsas the S-polarized light and the blue light beam BLp as the P-polarizedlight mixed with each other with a predetermined ratio. Specifically,the blue light beams BLs as the S-polarized light emitted from the lightemitting elements 211 enter the second retardation element 2131, and theblue light including the blue light beam BLs as the S-polarized lightand the blue light beam BLp as the P-polarized light is emitted from thesecond retardation element 2131.

By the rotation device 2132 adjusting the rotational angle of the secondretardation element 2131, there is adjusted the ratio between the lightintensity of the blue light beam BLs as the S-polarized light includedin the light beam having been transmitted through the second retardationelement 2131 and the light intensity of the blue light beam BLp as theP-polarized light included in the light beam having been transmittedthrough the second retardation element 2131. It should be noted thatwhen there is no need to adjust the ratio between the light intensity ofthe blue light beam BLs and the light intensity of the blue light beamBLp, the rotation device 2132 for rotating the second retardationelement 2131 is not required to be disposed. In that case, therotational angle of the second retardation element 2131 is set so thatthe ratio between the light intensity of the blue light beam BLs and thelight intensity of the blue light beam BLp becomes a predetermined lightintensity ratio, and then the rotational position of the secondretardation element 2131 is fixed.

In such a manner, the light source section 21 emits the blue lightincluding the blue light beam BLs as the S-polarized light and the bluelight beam BLp as the P-polarized light. It should be noted that in thepresent embodiment, there is adopted the configuration in which all ofthe light emitting elements 211 emit the blue light beam BLs as theS-polarized light, but it is possible to adopt a configuration in whichthe light emitting element 211 for emitting the blue light beam BLs asthe S-polarized light and the light emitting element 211 for emittingthe blue light beam BLp as the P-polarized light are mixed. According tothis configuration, it is also possible to omit the rotary retardationdevice 213. Further, it is also possible for the light emitting element211 to be formed of another solid-state light source such as an LED(Light Emitting Diode) instead of the semiconductor laser.

Configuration of Optical Element

The light beam including the blue light beam BLs as the S-polarizedlight and the blue light beam BLp as the P-polarized light enters theoptical element 22 along the +X direction. Although not shown in thedrawings, the optical element 22 is constituted by a substrate, and anoptical film formed on one surface of the substrate. Specifically, theoptical element 22 in the present embodiment is formed of a plate typeoptical element. The substrate is formed of, for example, generaloptical glass. The optical film is formed of, for example, a dielectricmultilayer film.

The optical film has a characteristic of transmitting the blue lightbeam BLp as the P-polarized light, transmitting the blue light beam BLsas the S-polarized light, and reflecting the yellow light beam YLs asthe S-polarized light toward the +Z direction. The substrate is tilted45° with respect to the X axis and the Z axis. In other words, thesubstrate is tilted 45° with respect to the X-Y plane and the Y-Z plane.Therefore, the optical element 22 transmits the blue light beam BLp asthe P-polarized light which enters the optical element 22 along the +Xdirection from the light source section toward the +X direction,transmits the blue light beam BLs as the S-polarized light toward the +Xdirection, and reflects the yellow light beam YLs as the S-polarizedlight which enters the optical element 22 along the −X direction fromthe polarization split element 23 described later toward the +Zdirection.

It is sufficient for the optical element 22 to have a characteristic ofreflecting at least the S-polarized light with respect to the wavelengthband of the yellow light, and whether or not the P-polarized light isreflected does not matter. It should be noted that it is possible forthe optical element 22 to have a characteristic of reflecting both ofthe S-polarized light and the P-polarized light with respect to thewavelength band of the yellow light. In other words, it is possible forthe optical element 22 to have a characteristic of transmitting light inthe blue wavelength band and reflecting light in the yellow wavelengthband irrespective of the polarization direction. In other words, theoptical element 22 can be formed of a dichroic mirror.

Further, the optical element 22 can be constituted by two base memberseach having an isosceles right triangular prismatic shape, and anoptical film disposed between tilted surfaces opposed to each other ofthe two base members. Specifically, the optical element 22 can be formedof a prism type optical element. It should be noted that as a result ofan experimental manufacture of the light source device according to thepresent embodiment, the inventors have confirmed that a good opticalcharacteristic can be obtained by the optical element 22 of the platetype.

Configuration of Polarization Split Element

The polarization split element 23 is disposed at the +X direction sideof the optical element 22. The blue light beam BLp as the P-polarizedlight transmitted through the optical element 22 and the blue light beamBLs as the S-polarized light transmitted through the optical element 22enter the polarization split element 23. The polarization split element23 is formed of a prism type polarization split element. Thepolarization split element 23 has two base members 232 and apolarization split layer 231 disposed between the two base members 232.

Specifically, each of the two base members 232 has a substantiallyisosceles right triangular prismatic shape. The two base members 232 arecombined with each other so that the tilted surfaces are opposed to eachother, and are formed to have a substantially rectangular solid shape asa whole. The polarization split layer 231 is disposed between the tiltedsurfaces of the two base members 232. The polarization split layer 231is tilted 45° with respect to the X axis and the Z axis. In other words,the polarization split layer 231 is tilted 45° with respect to the X-Yplane and the Y-Z plane. Further, the polarization split layer 231 isdisposed in parallel to the optical element 22.

The polarization split layer 231 has a polarization split characteristicof reflecting the S-polarized light and transmitting the P-polarizedlight. Therefore, the polarization split element 23 transmits the bluelight beam BLp as the P-polarized light which enters the polarizationsplit element 23 along the +X direction from the optical element 22toward the +X direction, and reflects the blue light beam BLs as theS-polarized light which enters the polarization split element 23 alongthe +X direction from the optical element 22 toward the −Z directioncrossing the +X direction. The polarization split layer 231 is formedof, for example, a dielectric multilayer film. The base members 232 areeach formed of general optical glass.

Configuration of First Retardation Element

The first retardation element 24 is disposed at the +X direction side ofthe polarization split element 23. Specifically, the first retardationelement 24 is disposed between the polarization split element 23 and adiffusion plate 261 on the X axis. The first retardation element 24 isformed of a ¼ wave plate with respect to the blue wavelength band of theblue light beam BLp which enters the first retardation element 24. Theblue light beam BLp as the P-polarized light having been transmittedthrough the polarization split element 23 is converted by the firstretardation element 24 into, for example, a blue light beam BLc1 asclockwise circularly polarized light, and is then emitted toward thefirst light collection element 25. In such a manner, the blue light beamBLp as the P-polarized light enters the first retardation element 24along the +X direction from the polarization split element 23, and thefirst retardation element 24 converts the polarization state of the bluelight beam BLp from the linearly polarized light into the circularlypolarized light.

Configuration of First Light Collection Element

The first light collection element 25 is disposed at the +X directionside of the first retardation element 24. In other words, the firstlight collection element 25 is disposed between the first retardationelement 24 and the diffusion device 26 on the X axis. The first lightcollection element 25 converges the blue light beam BLc1 which entersthe first light collection element 25 from the first retardation element24 on the diffusion plate 261 of the diffusion device 26. Further, thefirst light collection element 25 collimates a blue light beam BLc2described later which enters the first light collection element 25 fromthe diffusion device 26, and then emits the result toward the firstretardation element 24. In the example shown in FIG. 3, the first lightcollection element 25 is constituted by two convex lenses, namely afirst lens 251 and a second lens 252. It should be noted that the numberof the lenses constituting the first light collection element 25 is notparticularly limited.

Configuration of Diffusion Device

The diffusion device 26 is disposed at the +X direction side of thefirst light collection element 25. In other words, the diffusion device26 is disposed at the +X direction side of the polarization splitelement 23. The diffusion device 26 diffuses the blue light beam BLc1which enters the diffusion device 26 along the +X direction from thepolarization split element 23 via the first retardation element 24 andthe first light collection element 25 so that the diffusion anglebecomes equivalent to that of the yellow light beam YL which is emittedfrom the wavelength conversion element 28 described later, and thenemits the result toward the −X direction. The diffusion device 26 isprovided with the diffusion plate 261 and a rotation device 262. Thediffusion plate 261 preferably has a reflection characteristic as closeto the Lambertian scattering as possible, and reflects the blue lightbeam BLc1 having entered the diffusion plate 261 in a wide-angle manner.The rotation device 262 is formed of a motor and so on, and rotates thediffusion plate 261 centering on a rotational axis Rx parallel to the Xaxis.

The diffusion plate 261 in the present embodiment corresponds to adiffusion element in the appended claims.

The blue light beam BLc1 having entered the diffusion plate 261 isreflected by the diffusion plate 261 to thereby be converted into theblue light beam BLc2 as the circularly polarized light having anopposite rotational direction. In other words, the blue light beam BLc1as the clockwise circularly polarized light is converted by thediffusion plate 261 into the blue light beam BLc2 as counterclockwisecircularly polarized light. The blue light beam BLc2 emitted from thediffusion device 26 passes the first light collection element 25 towardthe −X direction, and then enters the first retardation element 24 onceagain. On this occasion, the blue light beam BLc2 which enters the firstretardation element 24 from the first light collection element 25 isconverted by the first retardation element 24 into the blue light beamBLs as the S-polarized light. The blue light beam BLs as the S-polarizedlight is reflected by the polarization split layer 231 of thepolarization split element 23 toward the +Z direction, and then entersthe first color separation element 29.

Configuration of Second Light Collection Element

The second light collection element 27 is disposed at the −Z directionside of the polarization split element 23. In other words, the secondlight collection element 27 is disposed between the polarization splitelement 23 and the wavelength conversion element 28 on the Z axis. Thesecond light collection element 27 converges the blue light beam BLsreflected by the polarization split element 23 on the wavelengthconversion element 28. Further, the second light collection element 27collimates the yellow light beam YL which is emitted from the wavelengthconversion element 28 and is described later, and then emits the resulttoward the polarization split element 23. In the example shown in FIG.3, the second light collection element 27 is constituted by two convexlenses, namely a first lens 271 and a second lens 272. It should benoted that the number of the lenses constituting the second lightcollection element 27 is not particularly limited.

Configuration of Wavelength Conversion Element

The wavelength conversion element 28 is disposed at the −Z directionside of the second light collection element 27. In other words, thewavelength conversion element 28 is disposed at the −Z direction side ofthe polarization split element 23. The wavelength conversion element 28is a reflective wavelength conversion element which is excited by thelight entering the wavelength conversion element, and emits light havinga different wavelength band from the wavelength band of the light havingentered the wavelength conversion element 28 toward an oppositedirection to the incident direction of the light. In other words, thewavelength conversion element 28 performs the wavelength conversion onthe light which enters the wavelength conversion element 28, and thenemits the light on which the wavelength conversion has been performedtoward the opposite direction to the incident direction of the light.

In the present embodiment, the wavelength conversion element 28 includesa yellow phosphor which is excited by blue light and emits yellow light.Specifically, the wavelength conversion element 28 includes, forexample, an yttrium aluminum garnet (YAG) type phosphor containingcerium (Ce) as an activator. The wavelength conversion element 28 emitsfluorescence having a yellow wavelength band longer than the bluewavelength band of the blue light beam BLs entering the wavelengthconversion element 28 along the −Z direction, namely the yellow lightbeam YL as unpolarized light, toward the +Z direction. The yellow lightbeam YL has a wavelength band of, for example, 500 through 650 nm. Theyellow light beam YL is light having a wavelength band including thegreen wavelength band and the red wavelength band. Therefore, thewavelength conversion element 28 performs the wavelength conversion onthe blue light beam BLs as the S-polarized light which enters thewavelength conversion element 28 along the −Z direction from thepolarization split element 23, and emits a second light beam having theyellow wavelength band different from the blue wavelength band towardthe +Z direction as an opposite direction to the −Z direction.

The fluorescence having the yellow wavelength band in the presentembodiment, namely the yellow light beam YL as the unpolarized light,corresponds to the second light beam having a second wavelength band inthe appended claims.

The yellow light beam YL emitted from the wavelength conversion element28 is transmitted through the second light collection element 27 alongthe +Z direction to thereby be collimated, and then enters thepolarization split element 23. Although the wavelength conversionelement 28 in the present embodiment is a stationary wavelengthconversion element, instead of this configuration, it is possible to usea rotary wavelength conversion element provided with a rotation devicefor rotating the wavelength conversion element 28 centering on arotational axis parallel to the Z axis. When using the rotary wavelengthconversion element, a rise in temperature of the wavelength conversionelement 28 is suppressed, and thus, it is possible to increase thewavelength conversion efficiency.

As described above, the polarization split layer 231 of the polarizationsplit element 23 has a polarization split characteristic of reflectingthe S-polarized light and transmitting the P-polarized light. Therefore,out of the yellow light beam YL as the unpolarized light having enteredthe polarization split layer 231, the yellow light beam YLs as theS-polarized light is reflected by the polarization split layer 231toward the −X direction, and then enters the optical element 22. Theyellow light beam YLs as the S-polarized light is reflected by theoptical element 22 toward the +Z direction, and then enters the secondcolor separation element 33.

Meanwhile, out of the yellow light beam YL as the unpolarized lighthaving entered the polarization split layer 231, the yellow light beamYLp as the P-polarized light is transmitted through the polarizationsplit layer 231 toward the +Z direction to be emitted from thepolarization split element 23, and then enters the first colorseparation element 29.

It should be noted that the yellow light beam YLp as the P-polarizedlight in the present embodiment corresponds to the second light beampolarized in the first polarization direction in the appended claims.The yellow light beam YLs as the S-polarized light corresponds to thesecond light beam polarized in the second polarization direction in theappended claims.

Configuration of First Color Separation Element

FIG. 5 is a side view of the light source device 2 viewed from the +Xdirection. In other words, FIG. 5 shows the state of the first colorseparation element 29 viewed from the +X direction. In FIG. 5, in orderto make the drawing eye-friendly, there is omitted the illustration ofthe second light collection element 27, the wavelength conversionelement 28, the first retardation element 24, the first light collectionelement 25, and the diffusion device 26 out of the constituents shown inFIG. 3.

As shown in FIG. 5, the first color separation element 29 is disposed atthe +Z direction side of the polarization split element 23. The firstcolor separation element 29 has a dichroic prism 291 and a reflectingprism 292. The dichroic prism 291 and the reflecting prism 292 arearranged side by side along the Y axis. The first color separationelement 29 separates light emitted toward the +Z direction from thepolarization split element 23 into the blue light beam BLs having theblue wavelength band and the yellow light beam YLp having the yellowwavelength band.

The blue light beam BLs having the blue wavelength band in the presentembodiment corresponds to a third light beam having the first wavelengthband in the appended claims. The yellow light beam YLp having the yellowwavelength band in the present embodiment corresponds to a fourth lightbeam having the second wavelength band in the appended claims.

The light including the blue light beam BLs and the yellow light beamYLp emitted from the polarization split element 23 enters the dichroicprism 291. The dichroic prism 291 is formed of a prism type colorseparation element formed by combining two base members each having asubstantially isosceles right triangular prismatic shape with each otherto form a substantially rectangular solid shape. On the interfacebetween the two base members, there is disposed a color separation layer2911. The color separation layer 2911 is tilted 45° with respect to theY axis and the Z axis. In other words, the color separation layer 2911is tilted 45° with respect to the X-Y plane and the X-Z plane.

The color separation layer 2911 functions as a dichroic mirror whichtransmits the blue light and reflects colored light having the yellowwavelength band different from the blue wavelength band, namely theyellow light, out of the light which enters the color separation layer2911. Therefore, the blue light beam BLs out of the light having enteredthe dichroic prism 291 along the +Z direction from the polarizationsplit element 23 is transmitted through the color separation layer 2911toward the +Z direction to be emitted outside the dichroic prism 291,and then enters the homogenization device 4 shown in FIG. 1.

In contrast, the yellow light beam YLp out of the light having enteredthe dichroic prism 291 along the +Z direction from the polarizationsplit element 23 is reflected toward the −Y direction by the colorseparation layer 2911. It should be noted that it is possible to adopt adichroic mirror having the color separation layer 2911 instead of thedichroic prism 291. Further, it is possible for the first colorseparation element 29 to have a configuration having a polarizationsplit element having a polarization split layer, and the reflectingprism 292. Even when a polarization split element which, for example,transmits the blue light beam BLs having entered the polarization splitelement toward the +Z direction, and reflects the yellow light beam YLpin the −Y direction toward the reflecting prism 292 is adopted in thefirst color separation element 29 instead of the dichroic prism 291, itis possible to separate the blue light beam BLs and the yellow lightbeam YLp from each other similarly to the first color separation element29 having the dichroic prism 291.

The reflecting prism 292 is disposed at the −Y direction side of thedichroic prism 291. The yellow light beam YLp reflected by the colorseparation layer 2911 enters the reflecting prism 292. The reflectingprism 292 is a prism type reflecting element formed by combining twobase members each having a substantially isosceles right triangularprismatic shape with each other to form a substantially rectangularsolid shape. On the interface between the two base members, there isdisposed a reflecting layer 2921. The reflecting layer 2921 is tilted45° with respect to the +Y direction and the +Z direction. In otherwords, the reflecting layer 2921 is tilted 45° with respect to the X-Yplane and the X-Z plane. In other words, the reflecting layer 2921 isdisposed in parallel to the color separation layer 2911.

The yellow light beam YLp which enters the reflecting layer 2921 alongthe −Y direction from the dichroic prism 291 is reflected toward the +Zdirection by the reflecting layer 2921. The yellow light beam YLpreflected by the reflecting layer 2921 is emitted from the reflectingprism 292 toward the +Z direction. It should be noted that it ispossible to adopt a reflecting mirror having the reflecting layer 2921instead of the reflecting prism 292.

Configuration of Reflecting Element

The reflecting element 31 is disposed at the +Z direction side of thereflecting prism 292. In other words, the reflecting element 31 isdisposed on the light path of the yellow light beam YLp emitted from thereflecting prism 292. The reflecting element 31 is formed of a halfmirror for transmitting a part of the light which enters the reflectingelement 31, and reflecting the rest of the light. It is sufficient forthe transmittance and the reflectance of the half mirror to arbitrarilybe set in accordance with the white balance of the light L to be emittedfrom the light source device 2, and for example, the transmittance isset to 80%, and the reflectance is set to 20%.

Therefore, a part of the yellow light beam YLp which has entered thereflecting element 31 is transmitted through the reflecting element 31,and is then emitted toward the fourth retardation element 30. Incontrast, another part of the yellow light beam YLs which has enteredthe reflecting element 31 is reflected by the reflecting element 31 toreenter the reflecting prism 292. The another part of the yellow lightbeam YLs having entered the reflecting prism 292 is reflected toward the+Y direction by the reflecting layer 2921, and then enters thewavelength conversion element 28 via the dichroic prism 291, thepolarization split element 23, and the second light collection element27.

The yellow phosphor included in the wavelength conversion element 28hardly absorbs the yellow light having entered the wavelength conversionelement 28 from the outside. Therefore, the yellow light beam YLp havingentered the wavelength conversion element 28 is repeatedly reflected ordiffused to thereby turn to the yellow light beam YL as the unpolarizedlight without being absorbed in the wavelength conversion element 28.The yellow light beam YL as the unpolarized light is emitted once againto the outside of the wavelength conversion element 28 together with theyellow light beam YL newly generated in the yellow phosphor. The yellowlight beam YL having been emitted from the wavelength conversion element28 enters the polarization split element 23 via the second lightcollection element 27 as described above. As described above, the ratiobetween the light intensity of the yellow light beam YLp transmittedthrough the reflecting element 31 and the light intensity of the yellowlight beam YLp reflected by the reflecting element 31 can be set inadvance. Further, the reflecting element 31 can be disposed so as tohave contact with a surface from which the yellow light beam YLp isemitted of the dichroic prism 292.

Configuration of Fourth Retardation Element

The fourth retardation element 30 is disposed at the +Z direction sideof the reflecting element 31. In other words, the fourth retardationelement 30 is disposed on the light path of the yellow light beam YLpemitted from the reflecting element 31. The fourth retardation element30 is formed of a ½ wave plate with respect to the yellow wavelengthband which the yellow light beam YLp has. The fourth retardation element30 converts the yellow light beam YLp as the P-polarized light emittedfrom the reflecting element 31 into the yellow light beam YLs as theS-polarized light. The yellow light beam YLs obtained by the conversioninto the S-polarized light by the fourth retardation element 30 isemitted toward the +Z direction from the light source device 2, and thenenters the homogenization device 4 shown in FIG. 1. Specifically, theyellow light beam YLs is spatially separated from the blue light beamBLs, and is emitted from an exit position different from the exitposition of the blue light beam BLs in the light source device 2, andthen enters the homogenization device 4. In particular, the yellow lightbeam YLs is emitted from the exit position distant toward the −Ydirection from the exit position of the blue light beam BLs in the lightsource device 2, and then enters the homogenization device 4.

Configuration of Second Color Separation Element

FIG. 4 is a side view of the light source device 2 viewed from the −Xdirection. In other words, FIG. 4 shows the state of the second colorseparation element 33 viewed from the −X direction. In FIG. 4, in orderto make the drawing eye-friendly, there is omitted the illustration ofthe rotary retardation device 213, the second light collection element27, the wavelength conversion element 28, and so on out of theconstituents shown in FIG. 3.

As shown in FIG. 4, the second color separation element 33 is disposedat the +Z direction side of the optical element 22. The second colorseparation element 33 has a dichroic prism 331 and a reflecting prism332. The dichroic prism 331 and the reflecting prism 332 are arrangedside by side along the Y axis. The second color separation element 33separates the yellow light beam YLs as the S-polarized light emittedtoward the +Z direction from the optical element 22 into the green lightbeam GLs in the green wavelength band different from the yellowwavelength band and the red light beam RLs in the red wavelength banddifferent from the yellow wavelength band and the green wavelength band.

The green light beam GLs in the green wavelength band in the presentembodiment corresponds to a fifth light beam having a third wavelengthband. The red light beam RLs in the red wavelength band in the presentembodiment corresponds to a sixth light beam having a fourth wavelengthband.

The dichroic prism 331 is formed of a prism type color separationelement similarly to the dichroic prism 291. On the interface betweenthe two base members, there is disposed a color separation layer 3311.The color separation layer 3311 is tilted 45° with respect to the +Ydirection and the +Z direction. In other words, the color separationlayer 3311 is tilted 45° with respect to the X-Y plane and the X-Zplane. The color separation layer 3311 is disposed in parallel to thereflecting layer 3321.

The color separation layer 3311 functions as a dichroic mirror fortransmitting the green light component of the incident light, andreflecting the red light component thereof. Therefore, the green lightbeam GLs as the S-polarized light out of the yellow light beam YLshaving entered the dichroic prism 331 is transmitted through the colorseparation layer 3311 toward the +Z direction to be emitted outside thedichroic prism 331. The green light beam GLs as the S-polarized light isemitted from the light source device 2 toward the +Z direction, and thenenters the homogenization device 4. In other words, the green light beamGLs is spatially separated from the blue light beam BLs and the yellowlight beam YLs, and is emitted from an exit position different from theexit positions of the blue light beam BLs and the yellow light beam YLs,and then enters the homogenization device 4. In other words, the greenlight beam GLs is emitted from the exit position distant toward the −Xdirection from the exit position of the blue light beam BLs in the lightsource device 2, and then enters the homogenization device 4.

In contrast, the red light beam RLs as the S-polarized light out of theyellow light beam YLs having entered the dichroic prism 331 is reflectedtoward the −Y direction by the color separation layer 3311. It should benoted that it is possible to use a dichroic mirror having the colorseparation layer 3311 instead of the dichroic prism 331.

The reflecting prism 332 has substantially the same configuration as thereflecting prism 292. Specifically, the reflecting prism 332 has areflecting layer 3321 which is parallel to the color separation layer2911, the color separation layer 3311, and the reflecting layer 2921.

The red light beam RLs which is reflected by the color separation layer3311, and then enters the reflecting layer 3321 is reflected by thereflecting layer 3321 toward the +Z direction. The red light beam RLshaving been reflected by the reflecting layer 3321 is emitted outsidethe reflecting prism 332. The red light beam RLs is emitted from thelight source device 2 toward the +Z direction, and then enters thehomogenization device 4. In other words, the red light beam RLs isspatially separated from the blue light beam BLs, the yellow light beamYLs, and the green light beam GLs, and is emitted from an exit positiondifferent from the exit positions of the blue light beam BLs, the yellowlight beam YLs, and the green light beam GLs, and then enters thehomogenization device 4. In other words, the red light beam RLs isemitted from the exit position which is distant toward the −Y directionfrom the exit position of the green light beam GLs in the light sourcedevice 2, and is distant toward the −X direction from the exit positionof the yellow light beam YLs, and then enters the homogenization device4.

Configuration of Homogenization Device

As shown in FIG. 1, the homogenization device 4 homogenizes theilluminance in the image formation area of the light modulation device 6irradiated with the light beams emitted from the light source device 2.The homogenization device 4 has a first multi-lens 41, a secondmulti-lens 42, and a superimposing lens 43.

The first multi-lens 41 has a plurality of lenses 411 arranged in amatrix in a plane perpendicular to a central axis of the light Lentering the first multi-lens 41 from the light source device 2, namelythe illumination light axis Ax. The first multi-lens 41 divides thelight entering the first multi-lens 41 from the light source device 2into a plurality of partial light beams with the plurality of lenses411.

FIG. 6 is a schematic diagram showing positions of incidence of therespective colored light beams in the first multi-lens 41 viewed fromthe −Z direction.

As shown in FIG. 6, the green light beam GLs, the red light beam RLs,the blue light beam BLs, and the yellow light beam YLs emitted from thelight source device 2 enter the first multi-lens 41. The green lightbeam GLs emitted from the position at the −X direction side and at the+Y direction side in the light source device 2 enters the plurality oflenses 411 included in an area A1 located at the −X direction side andat the +Y direction side in the first multi-lens 41. Further, the redlight beam RLs emitted from the position at the −X direction side and atthe −Y direction side in the light source device 2 enters the pluralityof lenses 411 included in an area A2 located at the −X direction sideand at the −Y direction side in the first multi-lens 41.

The blue light beam BLs emitted from the position at the +X directionside and at the +Y direction side in the light source device 2 entersthe plurality of lenses 411 included in an area A3 located at the +Xdirection side and at the +Y direction side in the first multi-lens 41.The yellow light beam YLs emitted from the position at the +X directionside and at the −Y direction side in the light source device 2 entersthe plurality of lenses 411 included in an area A4 located at the +Xdirection side and at the −Y direction side in the first multi-lens 41.Each of the colored light beams having entered the lenses 411 isconverted into a plurality of partial light beams, and enters lenses 421corresponding respectively to the lenses 411 in the second multi-lens42.

The blue light beam BLs out of the light beam L emitted from the lightsource device 2 according to the present embodiment corresponds to thethird light beam in the appended claims. The yellow light beam YLscorresponds to the fourth light beam in the appended claims. The greenlight beam GLs corresponds to the fifth light beam in the appendedclaims. The red light beam RLs corresponds to the sixth light beam inthe appended claims.

As shown in FIG. 1, the second multi-lens 42 has the plurality of lenses421 which is arranged in a matrix in a plane perpendicular to theillumination light axis Ax, and at the same time, correspondsrespectively to the plurality of lenses 411 of the first multi-lens 41.The partial light beams emitted from the lenses 411 opposed respectivelyto the lenses 421 enter the respective lenses 421. Each of the lenses421 makes the partial light beam enter the superimposing lens 43.

The superimposing lens 43 superimposes the plurality of partial lightbeams entering the superimposing lens 43 from the second multi-lens 42on each other in the image formation area of the light modulation device6. In particular, the second multi-lens 42 and the superimposing lens 43make the blue light beam BLs, the yellow light beam YLs, the green lightbeam GLs, and the red light beam RLs each divided into the plurality ofpartial light beams enter a plurality of microlenses 621 constituting amicrolens array 62 described later of the light modulation device 6 atrespective angles different from each other via the field lens 5.

Configuration of Light Modulation Device

As shown in FIG. 1, the light modulation device 6 modulates the lightemitted from the light source device 2. In particular, the lightmodulation device 6 modulates each of the colored light beams which areemitted from the light source device 2, and then enter the lightmodulation device 6 via the homogenization device 4 and the field lens 5in accordance with image information to form the image lightcorresponding to the image information. The light modulation device 6 isprovided with the single liquid crystal panel 61 and the singlemicrolens array 62.

Configuration of Liquid Crystal Panel

FIG. 7 is a schematic enlarged view of a part of the light modulationdevice 6 viewed from the −Z direction. In other words, FIG. 7 shows acorrespondence relationship between the pixels PX provided to the liquidcrystal panel 61 and the microlenses 621 provided to the microlens array62.

As shown in FIG. 7, the liquid crystal panel 61 has the plurality ofpixels PX arranged in a matrix in a plane perpendicular to theillumination light axis Ax (the Z axis).

One pixel PX has a plurality of sub-pixels SX for respectivelymodulating colored light beams different in color from each other. Inthe present embodiment, each of the pixels PX has four sub-pixels SX(SX1 through SX4). Specifically, in one pixel PX, the first sub-pixelSX1 is disposed at a position at the −X direction side and at the +Ydirection side. The second sub-pixel SX2 is disposed at a position atthe −X direction side and at the −Y direction side. The third sub-pixelSX3 is disposed at a position at the +X direction side and at the +Ydirection side. The fourth sub-pixel SX4 is disposed at a position atthe +X direction side and at the −Y direction side.

Configuration of Microlens Array

As shown in FIG. 1, the microlens array 62 is disposed at the −Zdirection side as the side of incidence of light with respect to theliquid crystal panel 61. The microlens array 62 guides the plurality ofcolored light beams entering the microlens array 62 to the individualpixels PX. The microlens array 62 has the plurality of microlenses 621corresponding to the plurality of pixels PX.

As shown in FIG. 7, the plurality of microlenses 621 is arranged in amatrix in a plane perpendicular to the illumination light axis Ax. Inother words, the plurality of microlenses 621 is arranged in a matrix inan orthogonal plane with respect to the central axis of the lightentering the plurality of microlenses 621 from the field lens 5. In thepresent embodiment, one microlens 621 is disposed so as to correspond tothe two sub-pixels arranged in the +X direction and the two sub-pixelsarranged in the +Y direction. In other words, one microlens 621 isdisposed so as to correspond to the four sub-pixels SX1 through SX4arranged 2×2 in the X-Y plane.

The blue light beam BLs, the yellow light beam YLs, the green light beamGLs, and the red light beam RLs superimposed by the homogenizationdevice 4 enter the microlenses 621 at respective angles different fromeach other. The microlenses 621 make the colored light beams enteringthe microlens 621 enter the sub-pixels SX corresponding to the coloredlight beams. Specifically, the microlens 621 makes the green light beamGLs enter the first sub-pixel SX1 out of the sub-pixels SX of the pixelPX corresponding to the microlens 621, makes the red light beam RLsenter the second sub-pixel SX2, makes the blue light beam BLs enter thethird sub-pixel SX3, and makes the yellow light beam YLs enter thefourth sub-pixel SX4. Thus, the colored light beams correspondingrespectively to the sub-pixels SX1 through SX4 enter the respectivesub-pixels SX1 through SX4, and the colored light beams are respectivelymodulated by the corresponding sub-pixels SX1 through SX4. In such amanner, the image light modulated by the liquid crystal panel 61 isprojected by the projection optical device 7 on the projection targetsurface such as a screen not shown.

Advantages of First Embodiment

In the related-art projector described in Document 1, the lamp is usedas the light source. Since the light emitted from the lamp is notuniform in polarization direction, in order to use the liquid crystalpanel as the light modulation device, a polarization conversion devicefor uniforming the polarization direction becomes necessary. For theprojector, there is generally used the polarization conversion deviceprovided with a multi-lens array and a polarization split element (PBS)array. However, in order to reduce the size of the projector, there arerequired the multi-lens array and the PBS array narrow in pitch, but itis extremely difficult to manufacture the PBS array narrow in pitch.

To cope with this problem, the light source device 2 according to thepresent embodiment is provided with the light source section 21 whichemits the blue light beams BLp, BLs having the blue wavelength band andrespectively including the P-polarized light and the S-polarized light,the optical element 22 which transmits the blue light beam BLp as theP-polarized light entering the optical element 22 along the +X directionfrom the light source section 21 toward the +X direction, and transmitsthe blue light beam BLs as the S-polarized light toward the +Xdirection, the polarization split element 23 which is disposed at the +Xdirection side of the optical element 22, transmits the blue light beamBLp as the P-polarized light entering the polarization split element 23along the +X direction from the optical element 22 toward the +Xdirection, and reflects the blue light beam BLs as the S-polarized lightentering the polarization split element 23 along the +X direction fromthe optical element 22 toward the −Z direction crossing the +Xdirection, the wavelength conversion element 28 which is disposed at the−Z direction side of the polarization split element 23, performs thewavelength conversion on the blue light beam BLs as the S-polarizedlight entering the wavelength conversion element 28 along the −Zdirection from the polarization split element 23 to emit the yellowlight beam YL having the yellow wavelength band different from the bluewavelength band toward the +Z direction as the opposite direction to the−Z direction, the diffusion plate 261 which is disposed at the +Xdirection side of the polarization split element 23, diffuses the bluelight beam BLc1 entering the diffusion plate 261 along the +X directionfrom the polarization split element 23, and emits the blue light beamBLc2 thus diffused toward the −X direction as the opposite direction tothe +X direction, the first color separation element 29 which isdisposed at the +Z direction side of the polarization split element 23,and separates the light emitted from the polarization split element 23into the blue light beam BLs having the blue wavelength band and theyellow light beam YLs having the yellow wavelength band, and the secondcolor separation element 33 which is disposed at the +Z direction sideof the optical element 22, and separates the yellow light beam YLsemitted from the optical element 22 into the green light beam GLs havingthe green wavelength band different from the yellow wavelength band, andthe red light beam RLs having the red wavelength band different from theyellow wavelength band and the green wavelength band, wherein thepolarization split element 23 transmits the yellow light beam YLp as theP-polarized light toward the +Z direction, and reflects the yellow lightbeam YLs as the S-polarized light toward the −X direction, and theoptical element 22 reflects the yellow light beam YLs as the S-polarizedlight which enters the optical element 22 along the −X direction fromthe polarization split element 23 toward the +Z direction.

In the present embodiment, the four colors of colored light beamsuniform in the polarization direction, namely the blue light beam BLs asthe S-polarized light, the yellow light beam YLs as the S-polarizedlight, the green light beam GLs as the S-polarized light, and the redlight beam RLs as the S-polarized light, are emitted from the lightsource device 2. According to this configuration, it is possible torealize the light source device 2 capable of emitting the plurality ofcolored light beams spatially separated from each other and uniformed inthe polarization direction without using the polarization conversionelement narrow in pitch described above. Thus, it becomes possible toreduce the light source device 2 in size, and by extension, it ispossible to achieve reduction in size of the projector 1.

Further, in the projector 1 according to the present embodiment, sincethe yellow light beam YLs enters the light modulation device 6 inaddition to the blue light beam BLs, the green light beam GLs, and thered light beam RLs, it is possible to increase the luminance of theimage projected from the projection optical device 7.

When considering the light source device with which substantially thesame advantages as described above can be obtained, it is conceivable toadopt a configuration in which, for example, two polarization splitelements consisting of the first polarization split element and thesecond polarization split element are arranged in sequence in the +Xdirection, the diffusion element is disposed at the −Z direction side ofthe first polarization split element, the wavelength conversion elementis disposed at the −Z direction side of the second polarization splitelement, and the four colored light beams obtained from the diffusionelement and the wavelength conversion element are emitted toward the +Zdirection on the condition that substantially the same light sourcesection as in the present embodiment is used. This light source devicewill hereinafter be referred to as a light source device according to acomparative example.

In the light source device according to the comparative example, it isnecessary to make the blue light beam BLs as the S-polarized lightreflected toward the −Z direction by the first polarization splitelement enter the diffusion element, and to make the second polarizationsplit element reflect the blue light beam BLp as the P-polarized lighttransmitted toward the +X direction through the first polarization splitelement toward the −Z direction to enter the wavelength conversionelement. In other words, it is necessary to transmit the blue light beamBLp as the P-polarized light in the first polarization split element onthe one hand, but it is necessary to reflect the blue light beam BLp asthe P-polarized light in the second polarization split element.

However, it is common for the polarization split film used in thepolarization split element to have a characteristic of reflecting theS-polarized light and transmitting the P-polarized light. Therefore,when realizing the light source device according to the comparativeexample, it is difficult to manufacture the second polarization splitelement for reflecting the blue light beam BLp as the P-polarized light.Specifically, in order to realize the characteristic described above, itis necessary to make the number of layers in the dielectric multilayerfilm which forms the polarization split film of the second polarizationsplit element extremely large, and it is difficult to form thedielectric multilayer film. Further, since the dielectric multilayerfilm extremely large in the number of layers is high in absorption oflight, there is a problem that a loss of light occurs. Further, in thecase of the present embodiment, since it is necessary for thepolarization split film of the second polarization split element to havea polarization split characteristic of reflecting the yellow light beamYLs as the S-polarized light and transmitting the yellow light beam YLpas the P-polarized light with respect to the yellow light beam YL, it ismore difficult to manufacture the polarization split film of reflectingthe P-polarized light with respect to the blue light while keeping thepolarization split characteristic with respect to the yellow light.

To cope with this problem, in the light source device 2 according to thepresent embodiment, it is sufficient for the optical element 22 to havea characteristic of transmitting both of the blue light beam BLp as theP-polarized light and the blue light beam BLs as the S-polarized light,and reflecting at least the yellow light beam YLs as the S-polarizedlight, and the optical element 22 can be formed of a dichroic mirror.Further, it is sufficient for the polarization split element 23 to havea characteristic of transmitting the P-polarized light and reflectingthe S-polarized light with respect to both of the blue light and theyellow light, and thus, the polarization split element 23 can be formedof a general polarization split element. As described above, in thelight source device 2 according to the present embodiment, since aspecial characteristic such as a characteristic of reflecting theP-polarized light is not required for the dielectric multilayer filmwhich forms the optical element 22 and the polarization split element23, it is easy to form the dielectric multilayer film. Specifically,since it is possible to reduce the number of layers of the dielectricmultilayer film, it is possible to achieve reduction of themanufacturing cost and an improvement of the yield ratio. Further, it ispossible to manufacture the optical element 22 and the polarizationsplit element 23 excellent in light separation characteristic. Asdescribed above, according to the light source device 2 related to thepresent embodiment, it is possible to solve the problem described abovewhich the light source device according to the comparative example has.

Further, the light source device 2 according to the present embodimentis further provided with the first retardation element 24 which isdisposed between the polarization split element 23 and the diffusionplate 261, and which the blue light beam BLp as the P-polarized lightenters along the +X direction from the polarization split element 23.

According to this configuration, it is possible to convert the bluelight beam BLc2 as the circularly polarized light having been emittedfrom the diffusion plate 261 with the first retardation element 24 intothe blue light beam BLs as the S-polarized light, and to reflect theresult with the polarization split layer 231 of the polarization splitelement 23. Thus, it is possible to increase the use efficiency of theblue light beam BLc2 emitted from the diffusion plate 261.

Further, in the light source device 2 according to the presentembodiment, the light source section 21 has the light emitting elements211 for emitting the blue light beams BLs having the blue wavelengthband, and the second retardation element 2131 which the blue light beamsBLs emitted from the light emitting elements 211 enter, and which emitsthe blue light including the blue light beam BLs as the S-polarizedlight and the blue light beam BLp as the P-polarized light.

According to this configuration, it is possible to surely make the bluelight beam BLp as the P-polarized light and the blue light beam BLs asthe S-polarized light enter the optical element 22. Further, accordingto this configuration, since the polarization directions of the lightbeams emitted from the plurality of light emitting elements 211 areallowed to be the same, it is sufficient to dispose the same solid-statelight sources in the same orientation, and thus, it is possible tosimplify the configuration of the light source section 21.

Further, in the light source device 2 according to the presentembodiment, there is adopted the configuration in which the secondretardation element 2131 can rotate centering on the rotational axisextending along the proceeding direction of the blue light beam BLsentering the second retardation element 2131.

According to this configuration, by adjusting the rotational angle ofthe second retardation element 2131, it is possible to adjust the ratiobetween the light intensity of the blue light beam BLs which enters theoptical element 22 and the light intensity of the blue light beam BLpwhich enters the optical element 22. Thus, it is possible to adjust thelight intensity ratio between the blue light beam BLs, and the yellowlight beam YLs, the green light beam GLs, and the red light beam RLsemitted from the light source device 2, and therefore, it is possible toadjust the white balance of the light source device 2.

Further, in the light source device 2 according to the presentembodiment, there is disposed the fourth retardation element 30 formedof the ½ wave plate with respect to the yellow wavelength band at the +Zdirection side of the reflecting prism 292.

According to this configuration, it is possible to convert the yellowlight beam YLp as the P-polarized light emitted from the reflectingprism 292 into the yellow light beam YLs as the S-polarized light. Thus,it is possible to uniform all of the blue light beam BLs, the yellowlight beam YLs, the green light beam GLs, and the red light beam RLsemitted from the light source device 2 into the S-polarized light.

Further, in the light source device 2 according to the presentembodiment, the reflecting element 31 for reflecting a part of theyellow light beam YLs is disposed at the light exit side of the yellowlight beam YLp in the first color separation element 29.

According to this configuration, by using the reflecting elements 31different in reflectance from each other, it is possible to adjust theratio in light intensity between the yellow light beam YLs, and thegreen light beam GLs and the red light beam RLs emitted from the lightsource device 2. Thus, it is possible to adjust the white balance of thelight source device 2. Further, by increasing the ratio of the lightintensity of the yellow light beam YLs to the light intensity of othercolored light beams, it is possible to increase the luminance of theprojection image. Further, by increasing the ratio of the lightintensity of the green light beam GLs and the red light beam RLs to thelight intensity of other colored light beams, it is possible to increasethe color reproducibility of the projection image.

Further, the light source device 2 according to the present embodimentis provided with the first light collection element 25 for collectingthe blue light beam BLc1 toward the diffusion device 26.

According to this configuration, it is possible to efficiently convergethe blue light beam BLc1 emitted from the first retardation element 24on the diffusion device 26 with the first light collection element 25,and at the same time, it is possible to collimate the blue light beamBLc2 emitted from the diffusion device 26. Thus, it is possible tosuppress the loss of the blue light beam BLs, and therefore, it ispossible to increase the use efficiency of the blue light beam BLs.

Further, the light source device 2 according to the present embodimentis provided with the second light collection element 27 for collectingthe blue light beam BLs toward the wavelength conversion element 28.

According to this configuration, it is possible to efficiently convergethe blue light beam BLs emitted from the polarization split element 23on the wavelength conversion element 28 with the second light collectionelement 27, and at the same time, it is possible to collimate the yellowlight beam YL emitted from the wavelength conversion element 28. Thus,it is possible to suppress the loss of the blue light beam BLp and theyellow light beam YL, and therefore, it is possible to increase the useefficiency of the blue light beam BLp and the yellow light beam YL.

The projector 1 according to the present embodiment is provided with thelight source device 2 according to the present embodiment, the lightmodulation device 6 for modulating the light emitted from the lightsource device 2 in accordance with the image information, and theprojection optical device 7 for projecting the light modulated by thelight modulation device 6.

According to this configuration, it is possible to realize the projector1 of a single plate type small in size and excellent in light useefficiency.

Further, the projector 1 according to the present embodiment is providedwith the homogenization device 4 located between the light source device2 and the light modulation device 6.

According to this configuration, it is possible to substantiallyuniformly illuminate the light modulation device 6 with the blue lightbeam BLs, the yellow light beam YLs, the green light beam GLs, and thered light beam RLs emitted from the light source device 2. Thus, it ispossible to suppress the color unevenness and the luminance unevennessin the projection image.

Further, in the projector 1 according to the present embodiment, thelight modulation device 6 is provided with the microlens array 62 havingthe plurality of microlenses 621 corresponding to the plurality ofpixels PX.

According to this configuration, it is possible to make the four coloredlight beams entering the light modulation device 6 enter thecorresponding four sub-pixels SX in the liquid crystal panel 61 with themicrolens 621. Thus, it is possible to make the colored light beamsemitted from the light source device 2 efficiently enter the respectivesub-pixels SX, and thus, it is possible to increase the use efficiencyof the colored light beams.

Second Embodiment

A second embodiment of the present disclosure will hereinafter bedescribed using FIG. 8 and FIG. 9.

A light source device according to the second embodiment issubstantially the same in basic configuration as that of the firstembodiment, but is different in configuration of the reflecting elementfrom that of the first embodiment. Therefore, the overall description ofthe light source device will be omitted.

FIG. 8 is a side view of a light source device 12 according to thesecond embodiment viewed from the +X direction. FIG. 9 is a schematicdiagram showing positions of incidence of colored light beams on amulti-lens. It should be noted that in FIG. 8, there is omitted theillustration of the second light collection element 27, the wavelengthconversion element 28, the first retardation element 24, the first lightcollection element 25, and the diffusion device 26.

In FIG. 8 and FIG. 9, the constituents common to the drawings used inthe first embodiment are denoted by the same reference symbols, and thedescription thereof will be omitted.

As shown in FIG. 8, the light source device 12 according to the presentembodiment is provided with a third color separation element 35 insteadof the reflecting element 31 in the light source device 2 according tothe first embodiment. Specifically, the third color separation element35 is disposed between the reflecting prism 292 and the fourthretardation element 30 on the light path of the yellow light beam YLpseparated by the first color separation element 29. The third colorseparation element 35 is formed of a dichroic mirror having acharacteristic of transmitting the green light beam GLp and reflectingthe red light beam RLp. It should be noted that it is also possible touse a dichroic prism as the third color separation element 35 instead ofthe dichroic mirror.

Therefore, the green light beam GLp included in the yellow light beamYLp which enters the third color separation element 35 from thereflecting prism 292 of the first color separation element 29 istransmitted through the third color separation element 35, converted bythe fourth retardation element 30 into a green light beam GLs2 as theS-polarized light, and then emitted outside the light source device 12.In other words, the light source device 12 emits the green light beamGLs2 instead of the yellow light beam YLs from the position where theyellow light beam YLs is emitted in the light source device 2 accordingto the first embodiment.

In the present embodiment, the green light beam GLs2 emitted from theposition where the yellow light beam YLs is emitted in the firstembodiment corresponds to the fourth light beam in the appended claims.

In contrast, a red light beam RLp2 included in the yellow light beam YLpwhich enters the third color separation element 35 is reflected by thethird color separation element 35 to enter the reflecting prism 292 fromthe +Z direction. Similarly to the yellow light beam YLp reflected bythe reflecting element 31 in the light source device 2 according to thefirst embodiment, the red light beam RLp2 returns to the wavelengthconversion element 28 via the first color separation element 29, thepolarization split element 23, and the second light collection element27.

As described above, since the yellow phosphor included in the wavelengthconversion element 28 hardly absorbs the yellow light beam havingentered the wavelength conversion element 28 from the outside, theyellow phosphor hardly absorbs the red light beam RLp2. Therefore, thered light beam RLp2 having entered the wavelength conversion element 28is repeatedly reflected inside the wavelength conversion element 28 tothereby turn to a red light beam as unpolarized light, and is thenemitted outside the wavelength conversion element 28 together with theyellow light beam YL generated by the yellow phosphor. The red lightbeam RLp as the P-polarized light out of the red light beam emitted fromthe wavelength conversion element 28 is transmitted through thepolarization split element 23, and then enters the first colorseparation element 29 once again to repeat the behavior described above.In contrast, the red light beam RLs as the S-polarized light out of thered light beam emitted from the wavelength conversion element 28 isreflected by the polarization split element 23 toward the −X direction,then reflected by the optical element 22 toward the +Z direction, and isthen emitted outside the light source device 12 via the second colorseparation element 33.

As shown in FIG. 9, the light source device 12 emits the blue light beamBLs, the green light beam GLs2, the green light beam GLs, and the redlight beam RLs. The green light beam GLs2 is emitted from the positionat the +X direction side and at the −Y direction side in the lightsource device 12, and then enters the plurality of lenses 411 disposedin the area A4 located at the +X direction side and at the −Y directionside in the first multi-lens 41. Although not shown in the drawings, thegreen light beam GLs2 enters the microlenses 621 via the firstmulti-lens 41, the second multi-lens 42, the superimposing lens 43, andthe field lens 5 similarly to the yellow light beam YLs in the firstembodiment. The green light beam GLs2 having entered each of themicrolenses 621 enters the fourth sub-pixel SX4 of the pixel PXcorresponding to that microlens 621.

Advantages of Second Embodiment

Also in the present embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the light source device 12 capable ofemitting the plurality of colored light beams made uniform inpolarization direction without using the polarization conversion elementnarrow in pitch, the advantage that it is possible to achieve thereduction in size of the light source device 12 and the projector 1, andthe advantage that it is easy to form the dielectric multilayer film,and it is possible to manufacture the optical element 22 and thepolarization split element 23 which are low in cost, and excellent inlight separation characteristic.

Further, in the light source device 12 according to the secondembodiment, since the green light beam GLs2 is emitted instead of theyellow light beam YLs in the light source device 2 according to thefirst embodiment, it is possible to increase the light intensity of thewhole of the green light which enters the pixel PX. Thus, it is possibleto increase the luminosity factor of the projection image.

It should be noted that it is possible to use a dichroic mirror having acharacteristic of reflecting the green light beam GLp and transmittingthe red light beam RLp as the third color separation element 35 incontrast to the present embodiment. Depending on the yellow phosphorincluded in the wavelength conversion element 28, the red light beamincluded in the yellow light beam YL emitted from the wavelengthconversion element 28 becomes insufficient in some cases. In this case,by using a dichroic mirror having the characteristic described above, itis possible to make the red light beam enter the second sub-pixel SX2and the fourth sub-pixel SX4 out of the four sub-pixels SX1 through SX4.Thus, it is possible to increase the color reproducibility of theprojection image.

Third Embodiment

A third embodiment of the present disclosure will hereinafter bedescribed using FIG. 10 through FIG. 13.

A light source device according to the third embodiment is substantiallythe same in basic configuration as that of the first embodiment, but isdifferent in configuration of the diffusion element, the wavelengthconversion element, and so on from that of the first embodiment.Therefore, the overall description of the light source device will beomitted.

FIG. 10 is a plan view of a light source device 13 according to thethird embodiment viewed from the +Y direction. FIG. 11 is a side view ofthe light source device 13 viewed from the −X direction. FIG. 12 is aside view of the light source device 13 viewed from the +X direction.FIG. 13 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

In FIG. 10 through FIG. 13, the constituents common to the drawings usedin the first embodiment are denoted by the same reference symbols, andthe description thereof will be omitted.

As shown in FIG. 10, the light source device 13 according to the presentembodiment has the light source section 21, an optical element 32, thepolarization split element 23, the first retardation element 24, thefirst light collection element 25, the diffusion device 26, the secondlight collection element 27, the wavelength conversion element 28, afirst color separation element 39, the reflecting element 31, a fourthretardation element 34, a third retardation element 36, and a secondcolor separation element 37. In the light source device 13 according tothe present embodiment, the positions of the diffusion device 26 and thewavelength conversion element 28 with respect to the polarization splitelement 23 are reversed from the positions of the diffusion device 26and the wavelength conversion element 28 with respect to thepolarization split element 23 in the first embodiment.

Configuration of Optical Element

In the case of the first embodiment, it is sufficient for the opticalelement 22 to have the characteristic of reflecting at least theS-polarized light with respect to the yellow wavelength band, andwhether or not the P-polarized light is reflected does not matter. Incontrast, it is necessary for the optical element 32 in the presentembodiment to reflect both of the S-polarized light and the P-polarizedlight with respect to the yellow wavelength band. Specifically, theoptical element 32 in the present embodiment is formed of a dichroicmirror having a characteristic of transmitting light in the bluewavelength band and reflecting light in the yellow wavelength bandirrespective of the polarization direction.

Configuration of Diffusion Device

The diffusion device 26 is disposed at the −Z direction side of thepolarization split element 23. The first retardation element 24 isdisposed between the polarization split element 23 and the diffusiondevice 26 on the Z axis. The blue light beam BLs as the S-polarizedlight enters the first retardation element 24 along the −Z directionfrom the polarization split element 23. The first light collectionelement 25 is disposed between the first retardation element 24 and thediffusion device 26 along the Z-axis direction.

The blue light beam BLs as the S-polarized light emitted from theoptical element 32 is reflected by the polarization split element 23,and is converted by the first retardation element 24 into the blue lightbeam BLc1 as the circularly polarized light. The blue light beam BLc1having entered the diffusion plate 261 is reflected by the diffusionplate 261 to thereby be converted into the blue light beam BLc2 as thecircularly polarized light having an opposite rotational direction. Theblue light beam BLc2 emitted from the diffusion device 26 reenters thefirst retardation element 24 to be converted into the blue light beamBLp as the P-polarized light. The blue light beam BLp as the P-polarizedlight is transmitted through the polarization split element 23 towardthe +Z direction, and then enters the first color separation element 39.

Configuration of Wavelength Conversion Element

The wavelength conversion element 28 is disposed at the +X directionside of the polarization split element 23. The second light collectionelement 27 is disposed between the polarization split element 23 and thewavelength conversion element 28 on the X axis.

The yellow light beam YL emitted from the wavelength conversion element28 is transmitted through the second light collection element 27 alongthe −X direction, and then enters the polarization split element 23. Outof the yellow light beam YL as the unpolarized light having entered thepolarization split layer 231 of the polarization split element 23, theyellow light beam YLs as the S-polarized light is reflected by thepolarization split layer 231 toward the +Z direction to be emitted fromthe polarization split element 23, and then enters the first colorseparation element 39.

Meanwhile, out of the yellow light beam YL as the unpolarized lighthaving entered the polarization split layer 231, the yellow light beamYLp as the P-polarized light is transmitted through the polarizationsplit layer 231 toward the −X direction, and then enters the opticalelement 32. The yellow light beam YLp as the P-polarized light isreflected by the optical element 32 toward the +Z direction, and thenenters the second color separation element 37.

Configuration of First Color Separation Element

As shown in FIG. 12, the first color separation element 39 is disposedat the +Z direction side of the polarization split element 23. The firstcolor separation element 39 has a dichroic prism 391 and the reflectingprism 292. The dichroic prism 391 and the reflecting prism 292 arearranged side by side along the Y axis. The first color separationelement 39 separates light emitted toward the +Z direction from thepolarization split element 23 into the blue light beam BLp having theblue wavelength band and the yellow light beam YLs having the yellowwavelength band.

The light including the blue light beam BLp and the yellow light beamYLs emitted from the polarization split element 23 enters the dichroicprism 391. The color separation layer 3911 functions as a dichroicmirror which transmits the yellow light and reflects the blue light outof the light entering the color separation layer 3911. Therefore, theyellow light beam YLs out of the light having entered the dichroic prism391 along the +Z direction from the polarization split element 23 istransmitted through the color separation layer 3911 toward the +Zdirection to be emitted outside the dichroic prism 391.

At the +Z direction side of the dichroic prism 391, there is disposedthe reflecting element 31 formed of a half mirror. A part of the yellowlight beam YLs which has entered the reflecting element 31 istransmitted through the reflecting element 31, and is then emittedoutside the light source device 13. The yellow light beam YLs is emittedfrom the light source device 13 toward the +Z direction, and then entersthe homogenization device 4 shown in FIG. 1. In contrast, another partof the yellow light beam YLs which has entered the reflecting element 31is reflected by the reflecting element 31 to enter the wavelengthconversion element 28 via the dichroic prism 391, the polarization splitelement 23, and the second light collection element 27. The behavior ofthe yellow light beam YLs having returned to the wavelength conversionelement 28 is substantially the same as in the first embodiment.

Meanwhile, the blue light beam BLp out of the light having entered thedichroic prism 391 is reflected by the color separation layer 3911toward the −Y direction, and then reflected by the reflecting layer 2921toward the +Z direction to be emitted outside the reflecting prism 292.

At the +Z direction side of the reflecting prism 292, there is disposedthe fourth retardation element 34. The fourth retardation element 34 isformed of a ½ wave plate with respect to the blue wavelength band whichthe blue light beam BLp has. The fourth retardation element 34 convertsthe blue light beam BLp as the P-polarized light emitted from thereflecting prism 292 into the blue light beam BLs as the S-polarizedlight. The blue light beam BLs obtained by the conversion into theS-polarized light by the fourth retardation element 34 is emitted towardthe +Z direction from the light source device 13, and then enters thehomogenization device 4 shown in FIG. 1.

Configuration of Third Retardation Element

The third retardation element 36 is disposed between the optical element32 and the second color separation element 37 on the Z axis. The thirdretardation element 36 is formed of a ½ wave plate with respect to theyellow wavelength band which the yellow light beam YLp has. The thirdretardation element 36 converts the yellow light beam YLp as theP-polarized light emitted from the optical element 32 toward the +Zdirection into the yellow light beam YLs as the S-polarized light. Theyellow light beam YLs as the S-polarized light emitted from the thirdretardation element 36 enters the second color separation element 37.

Configuration of Second Color Separation Element

As shown in FIG. 11, the second color separation element 37 is disposedat the +Z direction side of the optical element 32. The second colorseparation element 37 has a dichroic prism 371 and a reflecting prism332. The second color separation element 37 separates the yellow lightbeam YLs as the S-polarized light emitted toward the +Z direction fromthe third retardation element 36 into the green light beam GLs in thegreen wavelength band different from the yellow wavelength band and thered light beam RLs in the red wavelength band different from the yellowwavelength band and the green wavelength band.

The color separation layer 3711 of the dichroic prism 371 functions as adichroic mirror which transmits the red light component and reflects thegreen light component out of the light entering the color separationlayer 3711. Therefore, the red light beam RLs as the S-polarized lightout of the yellow light beam YLs having entered the dichroic prism 371is transmitted toward the +Z direction through the color separationlayer 3711 to be emitted outside the dichroic prism 371. The red lightbeam RLs as the S-polarized light is emitted toward the +Z directionfrom the light source device 13, and then enters the homogenizationdevice 4.

In contrast, the green light beam GLs as the S-polarized light out ofthe yellow light beam YLs having entered the dichroic prism 371 isreflected by the color separation layer 3711 toward the −Y direction,then reflected by the reflecting layer 3321 to be emitted outside thereflecting prism 332. The green light beam GLs is emitted toward the +Zdirection from the light source device 2, and then enters thehomogenization device 4.

In the case of the present embodiment, as shown in FIG. 13, the greenlight beam GLs, the red light beam RLs, the blue light beam BLs, and theyellow light beam YLs emitted from the light source device 13 enter thefirst multi-lens 41. The red light beam RLs enters the plurality oflenses 411 included in the area A1 at the −X direction side and at the+Y direction side in the first multi-lens 41. The green light beam GLsenters the plurality of lenses 411 included in the area A2 at the −Xdirection side and at the −Y direction side in the first multi-lens 41.The yellow light beam YLs enters the plurality of lenses 411 included inthe area A3 at the +X direction side and at the +Y direction side in thefirst multi-lens 41. The blue light beam BLs enters the plurality oflenses 411 included in the area A4 at the +X direction side and at the−Y direction side in the first multi-lens 41.

The rest of the configuration of the light source device 13 and theprojector 1 is substantially the same as in the first embodiment.

Advantages of Third Embodiment

The light source device 13 according to the present embodiment isprovided with the light source section 21 which emits the blue lightbeam having the blue wavelength band and including the blue light beamBLp as the P-polarized light and the blue light beam BLs as theS-polarized light, the optical element 32 which transmits the blue lightbeam BLp as the P-polarized light entering the optical element 32 alongthe +X direction from the light source section 21 toward the +Xdirection, and transmits the blue light beam BLs as the S-polarizedlight toward the +X direction, the polarization split element 23 whichis disposed at the +X direction side of the optical element 32,transmits the blue light beam BLp as the P-polarized light entering thepolarization split element 23 along the +X direction from the opticalelement 32 toward the +X direction, and reflects the blue light beam BLsas the S-polarized light entering the polarization split element 23along the +X direction from the optical element 22 toward the −Zdirection crossing the +X direction, the diffusion plate 261 which isdisposed at the −Z direction side of the polarization split element 23,diffuses the blue light beam BLc1 entering the diffusion plate 261 alongthe −Z direction from the polarization split element 23, and emits theblue light beam BLc2 thus diffused toward the +Z direction as theopposite direction to the −Z direction, the wavelength conversionelement 28 which is disposed at the +X direction side of thepolarization split element 23, performs the wavelength conversion on theblue light beam BLp as the P-polarized light entering the wavelengthconversion element 28 along the +X direction from the polarization splitelement 23 to emit the yellow light beam YL having the yellow wavelengthband different from the blue wavelength band toward the −X direction asthe opposite direction to the +X direction, the first color separationelement 39 which is disposed at the +Z direction side of thepolarization split element 23, and separates the light emitted from thepolarization split element 23 into the blue light beam BLp having theblue wavelength band and the yellow light beam YLs having the yellowwavelength band, and the second color separation element 37 which isdisposed at the +Z direction side of the optical element 32, andseparates the yellow light beam YLp emitted from the optical element 32into the green light beam GLs having the green wavelength band differentfrom the yellow wavelength band, and the red light beam RLs having thered wavelength band different from the yellow wavelength band and thegreen wavelength band, wherein the polarization split element 23transmits the yellow light beam YLp as the P-polarized light toward the−X direction, and reflects the yellow light beam YLs as the S-polarizedlight toward the +Z direction, and the optical element 32 reflects theyellow light beam YLp as the P-polarized light which enters the opticalelement 32 along the −X direction from the polarization split element 23toward the +Z direction.

Also in the present embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the light source device 13 capable ofemitting the plurality of colored light beams made uniform inpolarization direction without using the polarization conversion elementnarrow in pitch, the advantage that it is possible to achieve thereduction in size of the light source device 13 and the projector 1, andthe advantage that it is easy to form the dielectric multilayer film,and it is possible to manufacture the optical element 32 and thepolarization split element 23 which are low in cost, and excellent inlight separation characteristic.

Further, the light source device 13 according to the present embodimentis further provided with the first retardation element 24 which isdisposed between the polarization split element 23 and the diffusionplate 261, and which the blue light beam BLs as the S-polarized lightenters along the −Z direction from the polarization split element 23.

According to this configuration, it is possible to convert the bluelight beam BLc2 as the circularly polarized light having been emittedfrom the diffusion plate 261 with the first retardation element 24 intothe blue light beam BLp as the P-polarized light, and to transmit theresult through the polarization split layer 231 of the polarizationsplit element 23. Thus, it is possible to increase the use efficiency ofthe blue light beam BLc2 emitted from the diffusion plate 261.

Further, in the light source device 13 according to the presentembodiment, the light source section 21 has the light emitting elements211 for emitting the blue light beams BLs having the blue wavelengthband, and the second retardation element 2131 which the blue light beamsBLs emitted from the light emitting elements 211 enter, and which emitsthe blue light including the blue light beam BLp as the P-polarizedlight and the blue light beam BLs as the S-polarized light.

According to this configuration, it is possible to surely make the bluelight beam BLp as the P-polarized light and the blue light beam BLs asthe S-polarized light enter the optical element 32. Further, accordingto this configuration, since the polarization directions of the lightbeams emitted from the plurality of light emitting elements 211 areallowed to be the same, it is sufficient to dispose the same solid-statelight sources in the same orientation, and thus, it is possible tosimplify the configuration of the light source section 21.

Further, in the light source device 13 according to the presentembodiment, there is adopted the configuration in which the secondretardation element 2131 can rotate centering on the rotational axisextending along the proceeding direction of the blue light beam BLsentering the second retardation element 2131.

According to this configuration, by adjusting the rotational angle ofthe second retardation element 2131, it is possible to adjust the ratiobetween the light intensity of the blue light beam BLs which enters theoptical element 32 and the light intensity of the blue light beam BLpwhich enters the optical element 32. Thus, it is possible to adjust thelight intensity ratio between the blue light beam BLs, and the yellowlight beam YLs, the green light beam GLs, and the red light beam RLsemitted from the light source device 13, and therefore, it is possibleto adjust the white balance of the light source device 13.

Further, the light source device 13 according to the present embodimentis further provided with the third retardation element 36 for convertingthe yellow light beam YLp as the P-polarized light emitted from theoptical element 32 toward the +Z direction into the yellow light beamYLs as the S-polarized light.

According to this configuration, it is possible to convert the yellowlight beam YLp as the P-polarized light into the yellow light beam YLsas the S-polarized light with the third retardation element 36 at thetime point before the yellow light beam YLp enters the second colorseparation element 37. Therefore, it is possible to reduce the number ofthe retardation elements compared to when converting each of the redlight and the green light separated from each other by the second colorseparation element 37 from the P-polarized light into the S-polarizedlight.

Fourth Embodiment

A fourth embodiment of the present disclosure will hereinafter bedescribed using FIG. 14 and FIG. 15.

A light source device according to the fourth embodiment issubstantially the same in basic configuration as that of the thirdembodiment, but is different in configuration of the reflecting elementfrom that of the third embodiment. Therefore, the overall description ofthe light source device will be omitted.

FIG. 14 is a side view of a light source device 14 according to thefourth embodiment viewed from the +X direction. FIG. 15 is a schematicdiagram showing positions of incidence of colored light beams on themulti-lens. It should be noted that in FIG. 14, there is omitted theillustration of the second light collection element 27, the wavelengthconversion element 28, the first retardation element 24, the first lightcollection element 25, and the diffusion device 26.

In FIG. 14 and FIG. 15, the constituents common to the drawings used inthe third embodiment are denoted by the same reference symbols, and thedescription thereof will be omitted.

As shown in FIG. 14, the light source device 14 according to the presentembodiment is provided with a third color separation element 35 insteadof the reflecting element 31 in the light source device 13 according tothe third embodiment. Specifically, the third color separation element35 is disposed at the +Z direction side of the dichroic prism 391 on thelight path of the yellow light beam YLs separated by the first colorseparation element 39. The third color separation element 35 is formedof a dichroic mirror having a characteristic of transmitting the greenlight beam GLp and reflecting the red light beam RLp. It should be notedthat it is also possible to use a dichroic prism as the third colorseparation element 35 instead of the dichroic mirror.

Therefore, the green light beam GLs2 included in the yellow light beamYLs which enters the third color separation element 35 from the dichroicprism 391 of the first color separation element 39 is transmittedthrough the third color separation element 35 to be transmitted outsidethe light source device 14. In other words, the light source device 14according to the present embodiment emits the green light beam GLs2instead of the yellow light beam YLs from the position where the yellowlight beam YLs is emitted in the light source device 13 according to thethird embodiment.

In contrast, the red light beam RLs included in the yellow light beamYLs which enters the third color separation element 35 is reflected bythe third color separation element 35 to enter the polarization splitelement 23 from the −Z direction. The red light beam RLs2 returns to thewavelength conversion element 28 via the polarization split element 23and the second light collection element 27. The behavior of the redlight beam RLs having returned to the wavelength conversion element 28is substantially the same as in the second embodiment.

As shown in FIG. 15, the light source device 14 emits the blue lightbeam BLs, the green light beam GLs2, the green light beam GLs, and thered light beam RLs. The green light beam GLs2 is emitted from theposition at the +X direction side and at the +Y direction side in thelight source device 14, and then enters the plurality of lenses 411disposed in the area A3 located at the +X direction side and at the +Ydirection side in the first multi-lens 41. The green light beam GLs2enters the microlenses 621 via the first multi-lens 41, the secondmulti-lens 42, the superimposing lens 43, and the field lens 5 similarlyto the yellow light beam YLs in the third embodiment. The green lightbeam GLs2 having entered each of the microlenses 621 enters the thirdsub-pixel SX3 of the pixel PX corresponding to that microlens 621.

Advantages of Fourth Embodiment

Also in the present embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the light source device 14 capable ofemitting the plurality of colored light beams made uniform inpolarization direction without using the polarization conversion elementnarrow in pitch, the advantage that it is possible to achieve thereduction in size of the light source device 14 and the projector 1, andthe advantage that it is easy to form the dielectric multilayer film,and it is possible to manufacture the optical element 32 and thepolarization split element 23 which are low in cost, and excellent inlight separation characteristic.

Further, in the light source device 14 according to the presentembodiment, since the green light beam GLs2 is emitted instead of theyellow light beam YLs in the light source device 13 according to thethird embodiment, it is possible to increase the light intensity of thewhole of the green light which enters the pixel PX. Thus, it is possibleto increase the luminosity factor of the projection image.

It should be noted that it is possible to use a dichroic mirror having acharacteristic of reflecting the green light beam GLp and transmittingthe red light beam RLp as the third color separation element 35 incontrast to the present embodiment. In this case, by using a dichroicmirror having the characteristic described above, it is possible to makethe red light beam enter the second sub-pixel SX2 and the fourthsub-pixel SX4 out of the four sub-pixels SX1 through SX4. Thus, it ispossible to increase the color reproducibility of the projection image.

It should be noted that the scope of the present disclosure is notlimited to the embodiments described above, but a variety ofmodifications can be provided thereto within the scope or the spirit ofthe present disclosure.

For example, it is described in the first embodiment that the opticalelement can be the plate type or can also be the prism type, but theoptical element can be the plate type or can also be the prism type inother embodiments.

In each of the embodiments described above, the light source device isprovided with the first light collection element 25 and the second lightcollection element 27. However, this configuration is not a limitation,and at least one of the first light collection element 25 and the secondlight collection element 27 is not required to be disposed.

In each of the embodiments described above, the light source section 21emits the blue light beams BLs, BLp toward the +X direction. However,this is not a limitation, and it is also possible to adopt aconfiguration in which the light source section 21 emits the blue lightbeams BLs, BLp in a direction crossing the +X direction, and the bluelight beams BLs, BLp are reflected using, for example, a reflectingmember, and are then made to enter the optical element 22 in the +Xdirection.

In each of the embodiments described above, the projector is providedwith the homogenization device 4 having the first multi-lens 41, thesecond multi-lens 42, and the superimposing lens 43. It is possible todispose a homogenization device having other configurations instead ofthis configuration, or it is not required to dispose the homogenizationdevice 4.

The light source device according to each of the embodiments describedabove emits the colored light beams from the four exit positions,respectively, and the liquid crystal panel 61 constituting the lightmodulation device 6 has the four sub-pixels SX in each of the pixels PX.Instead of this configuration, it is possible to adopt a configurationin which the light source device emits three colored light beams, andthe liquid crystal panel has three sub-pixels in each pixel. In thiscase, for example, in the light source devices according to theembodiments described above, a total reflection member can be disposedin the light path of the yellow light beam YLs.

The light source device according to the first embodiment and the thirdembodiment emits the blue light beam BLs, the yellow light beam YLs, thegreen light beam GLs, and the red light beam RLs which are eachS-polarized light, and are spatially separated from each other. Further,the light source device according to the second embodiment and thefourth embodiment emits the blue light beam BLs, the green light beamGLs, and the red light beam RLs which are each S-polarized light, andare spatially separated from each other. Instead of theseconfigurations, the polarization state of the colored light beamsemitted by the light source device can be another polarization state.For example, it is possible for the light source device to have aconfiguration of emitting a plurality of colored light beams which areeach P-polarized light, and are spatially separated from each other.Further, the colored light beams emitted by the light source device arenot limited to the blue light beam, the yellow light beam, the greenlight beam, and the red light beam, but can also be other colored lightbeams. For example, the light source device can be provided with aconfiguration of emitting white light instead of the blue light and theyellow light.

Besides the above, the specific descriptions of the shape, the number,the arrangement, the material, and so on of the constituents of thelight source device and the projector are not limited to those of theembodiments described above, but can arbitrarily be modified. Further,although in the embodiments described above, there is described theexample of installing the light source device according to the presentdisclosure in the projector, the example is not a limitation. The lightsource device according to an aspect of the present disclosure can alsobe applied to lighting equipment, a headlight of a vehicle, and so on.

A light source device according to one aspect of the present disclosuremay have the following configuration.

The light source device according to the one aspect of the presentdisclosure includes a light source section configured to emit a firstlight beam which has a first wavelength band and includes lightpolarized in a first polarization direction and light polarized in asecond polarization direction different from the first polarizationdirection, an optical element which is configured to transmit the firstlight beam entering the optical element from the light source sectionalong a first direction and polarized in the first polarizationdirection toward the first direction, and is configured to transmit thefirst light beam polarized in the second polarization direction towardthe first direction, a polarization split element which is disposed atthe first direction side of the optical element, which is configured totransmit the first light beam entering the polarization split elementalong the first direction from the optical element and polarized in thefirst polarization direction toward the first direction, and which isconfigured to reflect the first light beam polarized in the secondpolarization direction toward a second direction crossing the firstdirection, a wavelength conversion element which is disposed at thesecond direction side of the polarization split element, which isconfigured to perform wavelength conversion on the first light beamentering the wavelength conversion element along the second directionfrom the polarization split element, and polarized in the secondpolarization direction, and which is configured to emit a second lightbeam having a second wavelength band different from the first wavelengthband toward a third direction as an opposite direction to the seconddirection, a diffusion element which is disposed at the first directionside of the polarization split element, and which is configured todiffuse the first light beam entering the diffusion element along thefirst direction from the polarization split element, and which isconfigured to emit the first light beam diffused toward a fourthdirection as an opposite direction to the first direction, a first colorseparation element which is disposed at the third direction side of thepolarization split element, and which is configured to separate lightemitted from the polarization split element into a third light beamhaving the first wavelength band and a fourth light beam having thesecond wavelength band, and a second color separation element which isdisposed at the third direction side of the optical element, and whichis configured to separate light emitted from the optical element into afifth light beam having a third wavelength band different from thesecond wavelength band, and a sixth light beam having a fourthwavelength band different from the second wavelength band and the thirdwavelength band, wherein the polarization split element transmits thesecond light beam polarized in the first polarization direction towardthe third direction and reflects the second light beam polarized in thesecond polarization direction toward the fourth direction, and theoptical element reflects the second light beam which enters the opticalelement along the fourth direction from the polarization split elementand which is polarized in the second polarization direction toward thethird direction.

In the light source device according to the one aspect of the presentdisclosure, there may further be included a first retardation elementwhich is disposed between the polarization split element and thediffusion element, and which the first light beam polarized in the firstpolarization direction enters along the first direction from thepolarization split element.

In the light source device according to the one aspect of the presentdisclosure, the light source section may include a light emittingelement configured to emit light having the first wavelength band, and asecond retardation element which the light having the first wavelengthband emitted from the light emitting element enters, and which isconfigured to emit the first light beam including light polarized in thefirst polarization direction and light polarized in the secondpolarization direction.

In the light source device according to the one aspect of the presentdisclosure, the second retardation element may be made rotatable arounda rotational axis along a proceeding direction of the light entering thesecond retardation element.

A light source device according to another aspect of the presentdisclosure includes a light source section configured to emit a firstlight beam which has a first wavelength band and includes lightpolarized in a first polarization direction and light polarized in asecond polarization direction different from the first polarizationdirection, an optical element which is configured to transmit the firstlight beam entering the optical element from the light source sectionalong a first direction and polarized in the first polarizationdirection toward the first direction, and is configured to transmit thefirst light beam polarized in the second polarization direction towardthe first direction, a polarization split element which is disposed atthe first direction side of the optical element, which is configured totransmit the first light beam entering the polarization split elementalong the first direction from the optical element and polarized in thefirst polarization direction toward the first direction, and which isconfigured to reflect the first light beam polarized in the secondpolarization direction toward a second direction crossing the firstdirection, a diffusion element which is disposed at the second directionside of the polarization split element, and which is configured todiffuse the first light beam entering the diffusion element along thesecond direction from the polarization split element, and which isconfigured to emit the first light beam diffused toward a thirddirection as an opposite direction to the second direction, a wavelengthconversion element which is disposed at the first direction side of thepolarization split element, which is configured to perform wavelengthconversion on the first light beam entering the wavelength conversionelement along the first direction from the polarization split element,and polarized in the first polarization direction, and which isconfigured to emit a second light beam having a second wavelength banddifferent from the first wavelength band toward a fourth direction as anopposite direction to the first direction, a first color separationelement which is disposed at the third direction side of thepolarization split element, and which is configured to separate lightemitted from the polarization split element into a third light beamhaving the first wavelength band and a fourth light beam having thesecond wavelength band, and a second color separation element which isdisposed at the third direction side of the optical element, and whichis configured to separate light emitted from the optical element into afifth light beam having a third wavelength band different from thesecond wavelength band, and a sixth light beam having a fourthwavelength band different from the second wavelength band and the thirdwavelength band, wherein the polarization split element transmits thesecond light beam polarized in the first polarization direction towardthe fourth direction and reflects the second light beam polarized in thesecond polarization direction toward the third direction, and theoptical element reflects the second light beam which enters the opticalelement along the fourth direction from the polarization split elementand which is polarized in the first polarization direction toward thethird direction.

In the light source device according to the another aspect of thepresent disclosure, there may further be included a first retardationelement which is disposed between the polarization split element and thediffusion element, and which the first light beam polarized in thesecond polarization direction enters along the second direction from thepolarization split element.

In the light source device according to the another aspect of thepresent disclosure, the light source section may include a lightemitting element configured to emit light having the first wavelengthband, and a second retardation element which the light having the firstwavelength band emitted from the light emitting element enters, andwhich is configured to emit the first light beam including lightpolarized in the first polarization direction and light polarized in thesecond polarization direction.

In the light source device according to the another aspect of thepresent disclosure, the second retardation element may be made rotatablearound a rotational axis along a proceeding direction of the lightentering the second retardation element.

In the light source device according to the another aspect of thepresent disclosure, there may further be included a third retardationelement configured to convert the second light beam which is emittedtoward the third direction from the optical element, and which ispolarized in the first polarization direction into the second light beampolarized in the second polarization direction.

A projector according to an aspect of the present disclosure may havethe following configuration.

The projector according to the aspect of the present disclosure includesthe light source device according to the one aspect of the presentdisclosure, a light modulation device configured to modulate light fromthe light source device in accordance with image information, and aprojection optical device configured to project the light modulated bythe light modulation device.

In the projector according to the aspect of the present disclosure,there may further be included a homogenization device disposed betweenthe light source device and the light modulation device, wherein thehomogenization device may include a pair of multi-lenses configured todivide the light entering the pair of multi-lenses from the light sourcedevice into a plurality of partial light beams, and a superimposing lensconfigured to superimpose the plurality of partial light beams enteringthe superimposing lens from the pair of multi-lenses on the lightmodulation device.

In the projector according to the aspect of the present disclosure, thelight modulation device may include a liquid crystal panel having aplurality of pixels, and a microlens array which is disposed at a lightincident side of the liquid crystal panel, and has a plurality ofmicrolenses corresponding to the plurality of pixels, the pixels mayeach include a first sub-pixel, a second sub-pixel, a third sub-pixel,and a fourth sub-pixel, and the microlens may make the third light beamenter the first sub-pixel, the fourth light beam enter the secondsub-pixel, the fifth light beam enter the third sub-pixel, and the sixthlight beam enter the fourth sub-pixel.

What is claimed is:
 1. A light source device comprising: a light sourcesection configured to emit a first light beam which has a firstwavelength band and includes light polarized in a first polarizationdirection and light polarized in a second polarization directiondifferent from the first polarization direction; an optical elementwhich is configured to transmit the first light beam entering theoptical element from the light source section along a first directionand polarized in the first polarization direction toward the firstdirection, and is configured to transmit the first light beam polarizedin the second polarization direction toward the first direction; apolarization split element which is disposed at the first direction sideof the optical element, which is configured to transmit the first lightbeam entering the polarization split element along the first directionfrom the optical element and polarized in the first polarizationdirection toward the first direction, and which is configured to reflectthe first light beam polarized in the second polarization directiontoward a second direction crossing the first direction; a wavelengthconversion element which is disposed at the second direction side of thepolarization split element, which is configured to perform wavelengthconversion on the first light beam entering the wavelength conversionelement along the second direction from the polarization split element,and polarized in the second polarization direction, and which isconfigured to emit a second light beam having a second wavelength banddifferent from the first wavelength band toward a third direction as anopposite direction to the second direction; a diffusion element which isdisposed at the first direction side of the polarization split element,and which is configured to diffuse the first light beam entering thediffusion element along the first direction from the polarization splitelement, and which is configured to emit the first light beam diffusedtoward a fourth direction as an opposite direction to the firstdirection; a first color separation element which is disposed at thethird direction side of the polarization split element, and which isconfigured to separate light emitted from the polarization split elementinto a third light beam having the first wavelength band and a fourthlight beam having the second wavelength band; and a second colorseparation element which is disposed at the third direction side of theoptical element, and which is configured to separate light emitted fromthe optical element into a fifth light beam having a third wavelengthband different from the second wavelength band, and a sixth light beamhaving a fourth wavelength band different from the second wavelengthband and the third wavelength band, wherein the polarization splitelement transmits the second light beam polarized in the firstpolarization direction toward the third direction and reflects thesecond light beam polarized in the second polarization direction towardthe fourth direction, and the optical element reflects the second lightbeam which enters the optical element along the fourth direction fromthe polarization split element and which is polarized in the secondpolarization direction toward the third direction.
 2. The light sourcedevice according to claim 1, further comprising: a first retardationelement which is disposed between the polarization split element and thediffusion element, and which the first light beam polarized in the firstpolarization direction enters along the first direction from thepolarization split element.
 3. The light source device according toclaim 1, wherein the light source section includes a light emittingelement configured to emit light having the first wavelength band, and asecond retardation element which the light having the first wavelengthband emitted from the light emitting element enters, and which isconfigured to emit the first light beam including light polarized in thefirst polarization direction and light polarized in the secondpolarization direction.
 4. The light source device according to claim 3,wherein the second retardation element is made rotatable around arotational axis along a proceeding direction of the light entering thesecond retardation element.
 5. A light source device comprising: a lightsource section configured to emit a first light beam which has a firstwavelength band and includes light polarized in a first polarizationdirection and light polarized in a second polarization directiondifferent from the first polarization direction; an optical elementwhich is configured to transmit the first light beam entering theoptical element from the light source section along a first directionand polarized in the first polarization direction toward the firstdirection, and is configured to transmit the first light beam polarizedin the second polarization direction toward the first direction; apolarization split element which is disposed at the first direction sideof the optical element, which is configured to transmit the first lightbeam entering the polarization split element along the first directionfrom the optical element and polarized in the first polarizationdirection toward the first direction, and which is configured to reflectthe first light beam polarized in the second polarization directiontoward a second direction crossing the first direction; a diffusionelement which is disposed at the second direction side of thepolarization split element, and which is configured to diffuse the firstlight beam entering the diffusion element along the second directionfrom the polarization split element, and which is configured to emit thefirst light beam diffused toward a third direction as an oppositedirection to the second direction; a wavelength conversion element whichis disposed at the first direction side of the polarization splitelement, which is configured to perform wavelength conversion on thefirst light beam entering the wavelength conversion element along thefirst direction from the polarization split element, and polarized inthe first polarization direction, and which is configured to emit asecond light beam having a second wavelength band different from thefirst wavelength band toward a fourth direction as an opposite directionto the first direction; a first color separation element which isdisposed at the third direction side of the polarization split element,and which is configured to separate light emitted from the polarizationsplit element into a third light beam having the first wavelength bandand a fourth light beam having the second wavelength band; and a secondcolor separation element which is disposed at the third direction sideof the optical element, and which is configured to separate lightemitted from the optical element into a fifth light beam having a thirdwavelength band different from the second wavelength band, and a sixthlight beam having a fourth wavelength band different from the secondwavelength band and the third wavelength band, wherein the polarizationsplit element transmits the second light beam polarized in the firstpolarization direction toward the fourth direction and reflects thesecond light beam polarized in the second polarization direction towardthe third direction, and the optical element reflects the second lightbeam which enters the optical element along the fourth direction fromthe polarization split element and which is polarized in the firstpolarization direction toward the third direction.
 6. The light sourcedevice according to claim 5, further comprising: a first retardationelement which is disposed between the polarization split element and thediffusion element, and which the first light beam polarized in thesecond polarization direction enters along the second direction from thepolarization split element.
 7. The light source device according toclaim 5, wherein the light source section includes a light emittingelement configured to emit light having the first wavelength band, and asecond retardation element which the light having the first wavelengthband emitted from the light emitting element enters, and which isconfigured to emit the first light beam including light polarized in thefirst polarization direction and light polarized in the secondpolarization direction.
 8. The light source device according to claim 7,wherein the second retardation element is made rotatable around arotational axis along a proceeding direction of the light entering thesecond retardation element.
 9. The light source device according toclaim 5, further comprising: a third retardation element configured toconvert the second light beam which is emitted toward the thirddirection from the optical element, and which is polarized in the firstpolarization direction into the second light beam polarized in thesecond polarization direction.
 10. A projector comprising: the lightsource device according to claim 1; a light modulation device configuredto modulate light from the light source device in accordance with imageinformation; and a projection optical device configured to project thelight modulated by the light modulation device.
 11. The projectoraccording to claim 10, further comprising: a homogenization devicedisposed between the light source device and the light modulationdevice, wherein the homogenization device includes a pair ofmulti-lenses configured to divide the light entering the pair ofmulti-lenses from the light source device into a plurality of partiallight beams, and a superimposing lens configured to superimpose theplurality of partial light beams entering the superimposing lens fromthe pair of multi-lenses on the light modulation device.
 12. Theprojector according to claim 11, wherein the light modulation deviceincludes a liquid crystal panel having a plurality of pixels, and amicrolens array which is disposed at a light incident side of the liquidcrystal panel, and has a plurality of microlenses corresponding to theplurality of pixels, the pixels each include a first sub-pixel, a secondsub-pixel, a third sub-pixel, and a fourth sub-pixel, and the microlensmakes the third light beam enter the first sub-pixel, the fourth lightbeam enter the second sub-pixel, the fifth light beam enter the thirdsub-pixel, and the sixth light beam enter the fourth sub-pixel.